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  • 3801.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering. University of Oulu, Finland, SenSiC AB, Kista, Sweden .
    Bastuck, Manuel
    Saarland University, Lab for Measurement Technology, Germany.
    Huotari, Joni
    University of Oulu, Finland.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering. University of Oulu, Finland.
    Lappalainen, Jyrki
    University of Oulu, Finland.
    Schuetze, Andreas
    Saarland University, Germany.
    Puglisi, Donatella
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    SiC-FET sensors for selective and quantitative detection of VOCs down to ppb level2016In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 168, p. 216-220Article in journal (Refereed)
    Abstract [en]

    With the increased interest in development of cheap, simple means for indoor air quality monitoring, and specifically in relation to certain well-known pollutant substances with adverse health effects even at very low concentrations, such as different Volatile Organic Compounds (VOCs), this contribution aims at providing an overview of the development status of the silicon carbide field effect transistor (SiC FET) based sensor platform for ppb level detection of VOCs. Optimizing the transducer design, the gas-sensitive material(s) composition, structure and processing, its mode of operation - applying temperature cycled operation in conjunction with multivariate data evaluation - and long-term performance it has been possible to demonstrate promising resultsregarding the sensor technology’s ability to achieve both single-digit ppb sensitivity towards e.g. naphthalene as well as selective detection of individual substances in a mixture of different VOCs.

  • 3802.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Bastuk, Manuel
    Saarland University, Saarbruecken, Germany.
    Huotari, Joni
    University of Oulu, Finland.
    Puglisi, Donatella
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Schütze, Andreas
    Saarland University, Saarbruecken, Germany.
    Lappalainen, Jyrki
    University of Oulu, Finland.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Optimization of the Field Effect Transistor transducer platform for the development of air quality sensors2016In: Proceedings EMRS 2016, 2016Conference paper (Refereed)
  • 3803.
    Andersson, Mike
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Becker, Elin
    Chalmers Tekniska Högskola.
    Lloyd Spetz, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Skoglund, Magnus
    Chalmers Tekniska Högskola.
    In situ DRIFT study of the CO response mechanism of MISFET sensors using Pt/SiO2 model sensor2008In: Proceedings of IEEE Sensors, IEEE , 2008, p. 1309-1312Conference paper (Refereed)
    Abstract [en]

    The temperature dependence of the sensor response towards CO of SiC-FET sensors has been studied by combining in situ DRIFT spectroscopy and sensor response measurements. The DRIFT spectroscopy studies have been performed on a model sensor representing the top layer of a SiC-FET sensor with porous Pt gate. Adsorbates on the model sensor have been studied at varying temperatures and gas concentrations, and correlated to sensor response measurements at similar experimental conditions. The results show that the temperature dependence partly can be correlated to the CO coverage of the surface. The switching point of the sensor response, observed at different temperatures depending on the CO and oxygen concentrations is well in accordance with the kinetics of the CO oxidation reaction.

  • 3804.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Buchholt, Kristina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Wingbrant, Helena
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    On the CO response mechanism of SiC based field effect gas sensorsManuscript (Other academic)
    Abstract [en]

    The response characteristics of Metal Insulator Silicon Carbide (MISiC) field effect sensor devices, with platinum (Pt) as the metal contact, towards carbon monoxide (CO) at varying oxygen (O2) concentrations and over a wide range of temperatures have been investigated in detail at atmospheric pressure. The influence of hydrogen (H2) on the CO response was also studied. Sensor devices with thin, porous as well as dense, homogeneous Pt films on top of both silicon dioxide (SiO2) and magnesium oxide (MgO) as insulator materials were investigated in this study. The reaction products generated on the sensor surfaces were also monitored with a mass spectrometer connected to the gas flow just downstream of the sensor location and the results compared to CO oxidation characteristics over Pt/SiO2 and to some extent Pt/MgO catalysts as reported in literature. By correlating the response characteristics of these devices with CO2 formation and hydrogen consumption on the sensor surfaces, strong indications for a CO response mechanism involving a CO induced increased sensitivity to background hydrogen have been obtained, this mechanism being hypothesized to be the only one behind the CO sensitivity of devices with dense Pt metal contacts. The results also give further support to the idea that also other processes than an increased sensitivity to background hydrogen contribute to the CO response of sensor devices with a porous platinum film as the metal contact, one candidate being the removal of oxygen anions from the surface of exposed oxide areas through the oxidation reaction with CO.

  • 3805.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Buchholt, Kristina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Wingbrant, Helena
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    On the response mechanism of SiC based field effect gas sensors towards non-hydrogen containing species and specifically NOManuscript (Other academic)
    Abstract [en]

    The response characteristics of Metal Insulator Silicon Carbide (MISiC) field effect sensor devices, with platinum (Pt) as the metal contact, towards nitrogen oxide (NO) for both low as well as relatively high background oxygen (O2) concentrations and different temperatures have been investigated at atmospheric pressure. Devices with both porous and dense Pt metal gate contacts have been investigated and the results seem to confirm the theories and results from earlier measurements regarding the requirement of porous metal films for the existence of a response to NO for this kind of sensor device. The results also suggest that no NO induced increased sensitivity to background hydrogen exists, at least it does not play any role in the observed NO sensitivity, as opposed to what has been suggested in the case of CO. The obtained results are also discussed in relation to some of the proposed sensing mechanisms for non-hydrogen containing substances and in comparison to NO reduction characteristics on Pt/SiO2 catalysts, as reported in literature. The results further give some indications about also some other process/ processes being important for the response of SiC based field effect sensors towards NO than just adsorption/desorption.

  • 3806.
    Andersson, Mike
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Everbrand, Lars
    Lloyd Spetz, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Nyström, T
    NIBE.
    Nilsson, M
    NIBE.
    Gauffin, C
    Svensson, H
    A MISiCFET based gas sensor system for combustion control in small-scale wood fired boilers2007In: IEEE Sensors,2007, 2007, p. 962-Conference paper (Refereed)
  • 3807.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Everbrand, Lars
    Nyström, Torkel
    Nilsson, Mikael
    Gauffin, Claes
    Svensson, Holger
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    A novel sensor system based on gas sensitive MISiCFET devices for combustion control in small-scale wood fired boilers2007Article in journal (Refereed)
  • 3808.
    Andersson, Mike
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Holmberg, Martin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Martensson, P.
    Paolesse, R.
    Department of Chemical Science and Technology, University of Rome (Tor Vergata), via della Ricerca Scientifica, 00133 Rome, Italy.
    Falconi, C.
    Department of Electronic Engineering, University of Rome (Tor Vergata), Via di Tor Vergata 110, 00133 Rome, Italy.
    Proietti, E.
    Department of Electronic Engineering, University of Rome (Tor Vergata), Via di Tor Vergata 110, 00133 Rome, Italy.
    Di, Natale C.
    Di Natale, C., Department of Electronic Engineering, University of Rome (Tor Vergata), Via di Tor Vergata 110, 00133 Rome, Italy.
    D'Amico, A.
    Department of Electronic Engineering, University of Rome (Tor Vergata), Via di Tor Vergata 110, 00133 Rome, Italy.
    Development of a ChemFET sensor with molecular films of porphyrins as sensitive layer2001In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 77, no 1-2, p. 567-571Article in journal (Refereed)
    Abstract [en]

    The interaction of chemical species with molecular films of porphyrins causes variations of the work function of the film itself, as it has been recently demonstrated by using the Kelvin probe technique. This characteristic makes porphyrins films suitable to be used as sensitive layers in ChemFET sensors. In this paper, we present a preliminary report about the fabrication and testing of such gas sensitive devices. The technological solutions towards an optimised device are also illustrated and discussed. © 2001 Elsevier Science B.V.

  • 3809.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ljung, Per
    Vattenfall Utveckling AB, Älvkarleby, Sweden.
    Mattsson, Mattias
    Vattenfall Utveckling AB, Älvkarleby, Sweden.
    Löfdahl, Mikael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Investigations on the possibilities of a MISiCFET sensor system for OBD and combustion control utilizing different catalytic gate materials2004In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 30-31, no 1, p. 365-368Article in journal (Refereed)
    Abstract [en]

    Different catalytic materials, like Pt and Ir, applied as gate contacts on metal insulator silicon carbide field effect transistors — MISiCFET—facilitate the manufacture of gas sensor devices with differences in selectivity, devices which due to the chemical stability and wide band gap of SiC are suitable for high temperature applications. The combination of such devices in a sensor system, utilizing multivariate analysis/modeling, have been tested and some promising results in respect of monitoring a few typical exhaust and flue gas constituents, in the future aiming at on board diagnostics (OBD) and combustion control, have been obtained.

  • 3810.
    Andersson, Mike
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Lloyd Spetz, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Detecting non-hydrogen containing species with field effect devices2008In: IEEE Sensors,2008, IEEE , 2008, p. 1320-1323Conference paper (Refereed)
    Abstract [en]

    An investigation of the influence and role of oxygen in the detection of non-hydrogen containing substances with Pt/SiO2/SiC based MOS field effect sensors, employing new model systems, has been carried out. With the use of a novel intermediate layer, by which the direct influence of hydrogen on the sensor response can be markedly reduced, the part of the sensor response which is not directly related to hydrogen (which to a small extent is always present in any gas mixture) could be resolved. The Pt/SiO2 NO reduction/oxidation model system has also been studied from a sensor perspective and the results compared to spectroscopic and mass spectrometry studies of the surface reactions from the field of catalysis. The results support the hypothesis from earlier work that the removal of oxygen from the sensor surface (e.g. by oxidation reactions with CO or NO) to a certain extent directly is involved in the detection of non-hydrogen containing species.

  • 3811.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Tailoring of field effect gas sensors for sensing of non-hydrogen containing substances from mechanistic studies on model systems2009Conference paper (Refereed)
    Abstract [en]

    To gain knowledge about the transduction mechanisms involved in the sensitivity of field effect gas sensors towards non-hydrogen containing substances, such as O-2, NO and CO, the sensor signal characteristics during exposure of some conceptually different model sensors to these as well as hydrogen containing gases have been investigated. The MOS capacitor based model sensors employ different combinations of insulator and contact materials, such as MgO, LaF3, IrO2 etc. The gas composition downstream of the sensor during test gas exposure at various conditions has also been studied by mass spectrometry (MS) and compared for the different model systems. The results have been compared to the characteristics of ordinary SiC/SiO2/Pt structures and from the information obtained a tailor made field effect sensor structure for oxygen sensing, to our knowledge for the first time with minimal interference from H-2, CO, and hydrocarbons, has been tested with promising results.

  • 3812.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Tailoring of SiC based field effect gas sensors for improved selectivity t non-hydrogen containing species2010In: IMCS13 2010, 2010, p. 369-Conference paper (Refereed)
  • 3813.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Technology and application opportunities for SiC-FET gas sensors2012In: Solid State Gas Sensors - Industrial Application / [ed] Maximilian Fleischer and Mirko Lehmann, Springer Berlin/Heidelberg, 2012, p. 189-214Chapter in book (Refereed)
    Abstract [en]

    The development of SiC-FET gas sensors has proceeded for about fifteen years. The maturity of the SiC material and a deeper understanding of the transduction mechanisms and sensor surface processes behind the sensitivity to a number of target substances have recently allowed the development of market-ready sensors for certain applications. Some examples presented below are a sensor system for domestic boiler control, an ammonia sensor for control of the SCR (selective catalytic reduction) and SNCR (Selective Non-Catalytic Reduction) NOx abatement processes as well as other more or less market-ready applications. In parallel, the basic research continues in order to reach more demanding markets/new applications and also to possibly lower the production costs of the sensors. Therefore, current research and future challenges are also treated, such as the development of new types of conducting ceramics for ohmic contacts to SiC in order to increase the operation temperature beyond the present state of the art.

  • 3814.
    Andersson, Mike
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lloyd Spetz, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Becker, Elin
    Skoglundh, Magnus
    Chalmers Tekniska Högskola.
    In Situ DRIFT study of hydrogen and CO adsorption on Pt/SiO2 model sensors2007In: IEEE Sensors,2007, 2007, p. 1028-Conference paper (Refereed)
  • 3815.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Mattsson, Mattias
    Vattenfall Utveckling AB, Älvkarleby, Sweden.
    Ljung, Per
    Vattenfall Utveckling AB, Älvkarleby, Sweden.
    On the applicability of MISiCFET gas sensors regarding ammonia slip monitoring in small-scale boilers running SNCR2007Manuscript (preprint) (Other academic)
    Abstract [en]

    Gas sensitive Metal Insulator Silicon Carbide Field Effect Transistor – MISiCFET – devices have shown good possibilities of realizing sensors for high temperature applications. One such application could be the monitoring of ammonia slip from boilers running SNCR – Selective Non-Catalytic Reduction of nitrogen oxides (NOx) with ammonia (NH3). In this study a number of MISiCFET gas sensors operated at different temperatures and with both platinum (Pt) and iridium (Ir) as the gate contact have been tested for their ability to detect and quantify ammonia slip in flue gases from a 5.6 MW wood fired boiler during a test of a new SNCR-system. The individual sensors have been evaluated and compared to each other for the sensitivity towards NH3 and possible cross-sensitivities to other flue gas species through the comparison of the sensor signals with the signals from analytical instruments like FTIR – Fourier Transform Infrared spectroscopy – for nitrogen oxides (NO + NO2), NH3, and carbon monoxide (CO) and an FID – Flame Ionization Detector – for the Total Hydrocarbon Concentration (THC). The ability of a combination of sensors to provide extra or more accurate information about the NH3 concentration was also evaluated through the construction and validation of a Partial Least Squares – PLS – regression model based on all the sensor signals. Under the assumption that the sensors’ responses follow a logarithmic dependence on NH3 concentration the results regarding  ammonia slip quantification were promising both for a single Ir sensor and for the system based on all sensors. There is still a question mark for the long-term stability of the devices in real flue gases, however.

  • 3816.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Pearce, Ruth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology. NPL, London from March 2012.
    Recent trends in Silicon Carbide (SiC) and Graphene based gas sensors2013In: Semiconductor Gas Sensors / [ed] R. Jaaniso and O. K. Tan, Woodhead Publishing Limited, 2013, p. 117-158Chapter in book (Refereed)
    Abstract [en]

    The introduction of silicon carbide (SiC) as the semiconductorin gas sensitive field effect devices has tremendously improved this sensor platform extending the temperature range and number of detectable gases. Here we review the recent trends in research, starting with transducer mechanisms, latest findings regarding the detection mechanism, and present new material combinations as sensing layers and smart operation of the field effect sensors enabling one sensor to act as a sensor array. Introducing epitaxially-grown graphene on SiC as gas sensing layer shows the potential of ppb detection of NO2 .

  • 3817.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Pearce, Ruth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Tunable gas alarms for high temperature applications based on 4H-SiC MISFET devices2011In: Proceedings of the International Conference on Silicon Carbide and Related materials, 2011, p. 365-Conference paper (Refereed)
  • 3818.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering. University of Oulu, Finland.
    Möller, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Fashandi, Hossein
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Puglisi, Donatella
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Huotari, J.
    University of Oulu, Finland.
    Puustinen, J.
    University of Oulu, Finland.
    Lappalainen, J.
    University of Oulu, Finland.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering. University of Oulu, Finland.
    Field Effect Based Gas Sensors, from Basic Mechanisms to the Latest Commercial Device Designs2016In: SENSORS AND ELECTRONIC INSTRUMENTATION ADVANCES (SEIA), INT FREQUENCY SENSOR ASSOC-IFSA , 2016, p. 19-21Conference paper (Refereed)
    Abstract [en]

    This contribution treats the latest developments in the understanding of basic principles regarding device design, transduction mechanisms, gas-materials-interactions, and materials processing for the tailored design and fabrication of SiC FET gas sensor devices, mainly intended as products for the automotive sector.

  • 3819.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    Pearce, Ruth
    National Physical Laboratory, Teddington, Middlesex, UK.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, The Institute of Technology.
    New generation SiC based field effect transistor gas sensors2013In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 179, no SI, p. 95-106Article in journal (Refereed)
    Abstract [en]

    With the advances in SiC processing and high temperature packaging technology over the past few years as well as the accumulation of knowledge regarding the sensing characteristics of different gate metal/insulator material combinations for different gaseous substances SiC based field effect high temperature sensors are moving towards commercial maturity. The route towards commercialization has, however, also led to the necessity of making new considerations regarding the basic transducer design and operation. The focus of this paper is thus the investigation of some basic transducer related parameters influence on sensor device performance, e.g. sensitivity and long-term stability, and characteristics to exemplify the importance of taking design, processing and operation parameters into account when developing field effect sensor devices for commercial applications. less thanbrgreater than less thanbrgreater thanTwo different types of devices, enhancement and depletion type MISFET sensors, with different gate dimensions and two different gate metallisations, Pt and Ir, have been processed. I/V-characteristics have been obtained under exposure to various concentrations of H-2, NH3, CO and O-2 and different bias conditions and the influence of gate dimensions and bias conditions on the sensitivity and dynamic range investigated. The long-term stability has also been studied and compared between different devices and bias conditions for conceptually different gas compositions. The results show that the type of basic transducer device, its design and mode of operation has a large influence on sensor performance. Depletion type devices offer better possibilities for tuning of sensitivity and dynamic range as well as improved longterm stability properties, whereas enhancement type devices require much less control of the processing to ensure good repeatability and yield. Some results have also been verified for two possible applications of SiC based field effect sensors, ammonia slip monitoring for the control of SCR/SNCR and combustion control in domestic/district heating facilities.

  • 3820.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Padban, Nader
    TPS Termiska Processer AB, Studsvik, Nyköping, Sweden.
    Larfeldt, Jenny
    TPS Termiska Processer AB, Studsvik, Nyköping, Sweden.
    Holmberg, Martin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    SiC-FE gas sensor based combustion control in domestic heating systems, characteristics and utility2007Manuscript (preprint) (Other academic)
    Abstract [en]

    SiC based field effect gas sensors have been evaluated for future possible use in combustion control schemes for domestic heating systems. Emphasis has been on the possibility to monitor the state of combustion and follow the development of the combustion process from an emissions point of view and to determine its cause. The sensor signals have been compared to true emissions data – CO and total hydrocarbon concentration – as obtained by an IR spectrometer and a flame ionization detector (FID) as well as flue gas concentration of oxygen as obtained by a paramagnetic cell. The sensor characteristics have been evaluated using multivariate statistics and the results suggest that, by using the signals from one or more SiC-based field effect sensors and a thermocouple, it seems possible to provide a rough picture of the state of combustion applicable to a control scheme in order to reduce emissions and increase the power to fuel economy.

  • 3821.
    Andersson, Mike
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Pardban, N.
    TPS Termiska Processer AB, Nyköping, Sweden.
    Larfeldt, J.
    TPS Termiska Processer AB, Nyköping, Sweden.
    Holmberg, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    The characteristics and utility of SiC-FE gas sensors for control of combustion in domestic heating systems [MISFET sensors]2004In: Proceedings of IEEE Sensors, 2004., 2004, p. 1157-1160Conference paper (Refereed)
    Abstract [en]

    The possible utility of MISiCFET gas sensors in the application of combustion control in small-scale boilers has been tested and compared to commercially available resistive-type MOS sensors. The results suggest that by using the signals from one or more MISiCFET sensors, together with the measured temperature of the furnace, it seems possible to provide a rough picture of the state of combustion applicable to a control scheme in order to reduce emissions and increase the power to fuel economy.

  • 3822.
    Andersson, Mike
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Wingbrant, Helena
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Study of CO response of SiC based field effect gas sensors2005In: IEEE Sensors 2005,2005, 2005, p. 105-Conference paper (Refereed)
  • 3823.
    Andersson, Monica
    Linköping University, Department of Management and Economics.
    Osäker vård? En fallstudie inom svensk hälso- och sjukvård2001Independent thesis Advanced level (degree of Magister)Student thesis
    Abstract [en]

    The swedish healthcare is in many situations one of the best in the world. But still, the healthcare system includes elemnts that reduce the efficiency. Partly becouse the swedish healthcare is largely monopolized, the servicecs are not properly prized and the economic responsibility and the liability legislation is limited. The main problem this study evolves around, is how a different liability rule would change the shape of the healthcare organisation. Abouve all, how would the approach to riskmanagement and preventive and riskreducing performance change with a diffrent liability rule. A quantitative investigation, with main focus on riskmanagement,have been made at two hospitals in Sweden. The reults show that the handling of an accident is inefficient and that the swedish healthcare involves more insecure elements than exepected.

  • 3824.
    Andersson, M.R.
    et al.
    Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Johansson, D.M.
    Department of Organic Chemistry, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Theander, M.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    The effect of the polymerisation temperature on molecular weight and photoluminescence quantum yield for a phenylsubstituted PPV2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 119, no 1-3, p. 63-64Article in journal (Refereed)
    Abstract [en]

    We present the synthesis and characterisation of poly(2-(2',5'-bis(2?-ethylhexyloxy)phenyl)-1, 4-phenylenevinylene) (BEHP-PPV) polymerised under different conditions. The photoluminescence efficiencies (?PL) in the solid state of BEHP-PPV obtained at 144°C and 0°C are 28% and 60%, respectively. Polymerisation temperatures below 0°C decreases the molecular weight without changing the photoluminescence efficiency to any large extent.

  • 3825.
    Andersson Naesseth, Christian
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Machine learning using approximate inference: Variational and sequential Monte Carlo methods2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Automatic decision making and pattern recognition under uncertainty are difficult tasks that are ubiquitous in our everyday life. The systems we design, and technology we develop, requires us to coherently represent and work with uncertainty in data. Probabilistic models and probabilistic inference gives us a powerful framework for solving this problem. Using this framework, while enticing, results in difficult-to-compute integrals and probabilities when conditioning on the observed data. This means we have a need for approximate inference, methods that solves the problem approximately using a systematic approach. In this thesis we develop new methods for efficient approximate inference in probabilistic models.

    There are generally two approaches to approximate inference, variational methods and Monte Carlo methods. In Monte Carlo methods we use a large number of random samples to approximate the integral of interest. With variational methods, on the other hand, we turn the integration problem into that of an optimization problem. We develop algorithms of both types and bridge the gap between them.

    First, we present a self-contained tutorial to the popular sequential Monte Carlo (SMC) class of methods. Next, we propose new algorithms and applications based on SMC for approximate inference in probabilistic graphical models. We derive nested sequential Monte Carlo, a new algorithm particularly well suited for inference in a large class of high-dimensional probabilistic models. Then, inspired by similar ideas we derive interacting particle Markov chain Monte Carlo to make use of parallelization to speed up approximate inference for universal probabilistic programming languages. After that, we show how we can make use of the rejection sampling process when generating gamma distributed random variables to speed up variational inference. Finally, we bridge the gap between SMC and variational methods by developing variational sequential Monte Carlo, a new flexible family of variational approximations.

    List of papers
    1. Capacity estimation of two-dimensional channels using Sequential Monte Carlo
    Open this publication in new window or tab >>Capacity estimation of two-dimensional channels using Sequential Monte Carlo
    2014 (English)In: 2014 IEEE Information Theory Workshop, 2014, p. 431-435Conference paper, Published paper (Refereed)
    Abstract [en]

    We derive a new Sequential-Monte-Carlo-based algorithm to estimate the capacity of two-dimensional channel models. The focus is on computing the noiseless capacity of the 2-D (1, ∞) run-length limited constrained channel, but the underlying idea is generally applicable. The proposed algorithm is profiled against a state-of-the-art method, yielding more than an order of magnitude improvement in estimation accuracy for a given computation time.

    National Category
    Control Engineering Computer Sciences Probability Theory and Statistics
    Identifiers
    urn:nbn:se:liu:diva-112966 (URN)10.1109/ITW.2014.6970868 (DOI)
    Conference
    Information Theory Workshop
    Available from: 2015-01-06 Created: 2015-01-06 Last updated: 2018-11-09
    2. Sequential Monte Carlo for Graphical Models
    Open this publication in new window or tab >>Sequential Monte Carlo for Graphical Models
    2014 (English)In: Advances in Neural Information Processing Systems, 2014, p. 1862-1870Conference paper, Published paper (Refereed)
    Abstract [en]

    We propose a new framework for how to use sequential Monte Carlo (SMC) algorithms for inference in probabilistic graphical models (PGM). Via a sequential decomposition of the PGM we find a sequence of auxiliary distributions defined on a monotonically increasing sequence of probability spaces. By targeting these auxiliary distributions using SMC we are able to approximate the full joint distribution defined by the PGM. One of the key merits of the SMC sampler is that it provides an unbiased estimate of the partition function of the model. We also show how it can be used within a particle Markov chain Monte Carlo framework in order to construct high-dimensional block-sampling algorithms for general PGMs.

    National Category
    Computer Sciences Probability Theory and Statistics Control Engineering
    Identifiers
    urn:nbn:se:liu:diva-112967 (URN)
    Conference
    Neural Information Processing Systems (NIPS)
    Available from: 2015-01-06 Created: 2015-01-06 Last updated: 2018-11-09Bibliographically approved
    3. Nested Sequential Monte Carlo Methods
    Open this publication in new window or tab >>Nested Sequential Monte Carlo Methods
    2015 (English)In: Proceedings of The 32nd International Conference on Machine Learning / [ed] Francis Bach, David Blei, Journal of Machine Learning Research (Online) , 2015, Vol. 37, p. 1292-1301Conference paper, Published paper (Refereed)
    Abstract [en]

    We propose nested sequential Monte Carlo (NSMC), a methodology to sample from sequences of probability distributions, even where the random variables are high-dimensional. NSMC generalises the SMC framework by requiring only approximate, properly weighted, samples from the SMC proposal distribution, while still resulting in a correct SMC algorithm. Furthermore, NSMC can in itself be used to produce such properly weighted samples. Consequently, one NSMC sampler can be used to construct an efficient high-dimensional proposal distribution for another NSMC sampler, and this nesting of the algorithm can be done to an arbitrary degree. This allows us to consider complex and high-dimensional models using SMC. We show results that motivate the efficacy of our approach on several filtering problems with dimensions in the order of 100 to 1 000.

    Place, publisher, year, edition, pages
    Journal of Machine Learning Research (Online), 2015
    Series
    JMLR Workshop and Conference Proceedings, ISSN 1938-7228 ; 37
    National Category
    Computer Sciences Control Engineering Probability Theory and Statistics
    Identifiers
    urn:nbn:se:liu:diva-122698 (URN)
    Conference
    32nd International Conference on Machine Learning, Lille, France, 6-11 July, 2015
    Available from: 2015-11-16 Created: 2015-11-16 Last updated: 2018-11-09Bibliographically approved
    4. Interacting Particle Markov Chain Monte Carlo
    Open this publication in new window or tab >>Interacting Particle Markov Chain Monte Carlo
    Show others...
    2016 (English)In: Proceedings of the 33rd International Conference on Machine Learning (ICML), 2016Conference paper, Published paper (Refereed)
    Abstract [en]

    We introduce interacting particle Markov chain Monte Carlo (iPMCMC), a PMCMC method based on an interacting pool of standard and conditional sequential Monte Carlo samplers. Like related methods, iPMCMC is a Markov chain Monte Carlo sampler on an extended space. We present empirical results that show significant improvements in mixing rates relative to both non-interacting PMCMC samplers and a single PMCMC sampler with an equivalent memory and computational budget. An additional advantage of the iPMCMC method is that it is suitable for distributed and multi-core architectures.

    Keywords
    Sequential Monte Carlo, Probabilistic programming, parallelisation
    National Category
    Computer Sciences Control Engineering Probability Theory and Statistics
    Identifiers
    urn:nbn:se:liu:diva-130043 (URN)
    Conference
    International Conference on Machine Learning (ICML), New York, USA, June 19-24, 2016
    Projects
    CADICS
    Funder
    Cancer and Allergy Foundation
    Available from: 2016-07-05 Created: 2016-07-05 Last updated: 2018-11-09
    5. Reparameterization Gradients through Acceptance-Rejection Sampling Algorithms
    Open this publication in new window or tab >>Reparameterization Gradients through Acceptance-Rejection Sampling Algorithms
    2017 (English)In: Proceedings of the 20th International Conference on Artificial Intelligence and Statistics, 2017Conference paper, Published paper (Refereed)
    Abstract [en]

    Variational inference using the reparameterization trick has enabled large-scale approximate Bayesian inference in complex probabilistic models, leveraging stochastic optimization to sidestep intractable expectations. The reparameterization trick is applicable when we can simulate a random variable by applying a differentiable deterministic function on an auxiliary random variable whose distribution is fixed. For many distributions of interest (such as the gamma or Dirichlet), simulation of random variables relies on acceptance-rejection sampling. The discontinuity introduced by the accept-reject step means that standard reparameterization tricks are not applicable. We propose a new method that lets us leverage reparameterization gradients even when variables are outputs of a acceptance-rejection sampling algorithm. Our approach enables reparameterization on a larger class of variational distributions. In several studies of real and synthetic data, we show that the variance of the estimator of the gradient is significantly lower than other state-of-the-art methods. This leads to faster convergence of stochastic gradient variational inference.

    Series
    Proceedings of Machine Learning Research, ISSN 1938-7228 ; 54
    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:liu:diva-152645 (URN)
    Conference
    Artificial Intelligence and Statistics, 20-22 April 2017, Fort Lauderdale, FL, USA
    Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2018-11-21
    6. Variational Sequential Monte Carlo
    Open this publication in new window or tab >>Variational Sequential Monte Carlo
    2018 (English)In: Proceedings of the Twenty-First International Conference on Artificial Intelligence and Statistics, 2018Conference paper, Published paper (Refereed)
    Abstract [en]

    Many recent advances in large scale probabilistic inference rely on variational methods. The success of variational approaches depends on (i) formulating a flexible parametric family of distributions, and (ii) optimizing the parameters to find the member of this family that most closely approximates the exact posterior. In this paper we present a new approximating family of distributions, the variational sequential Monte Carlo (VSMC) family, and show how to optimize it in variational inference. VSMC melds variational inference (VI) and sequential Monte Carlo (SMC), providing practitioners with flexible, accurate, and powerful Bayesian inference. The VSMC family is a variational family that can approximate the posterior arbitrarily well, while still allowing for efficient optimization of its parameters. We demonstrate its utility on state space models, stochastic volatility models for financial data, and deep Markov models of brain neural circuits.

    National Category
    Computer Sciences
    Identifiers
    urn:nbn:se:liu:diva-152646 (URN)
    Conference
    International Conference on Artificial Intelligence and Statistics, Playa Blanca, Lanzarote, Canary Islands, April 9 - 11, 2018
    Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2018-11-16Bibliographically approved
  • 3826.
    Andersson Naesseth, Christian
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nowcasting using Microblog Data2012Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    The explosion of information and user generated content made publicly available through the internet has made it possible to develop new ways of inferring interesting phenomena automatically. Some interesting examples are the spread of a contagious disease, earth quake occurrences, rainfall rates, box office results, stock market fluctuations and many many more. To this end a mathematical framework, based on theory from machine learning, has been employed to show how frequencies of relevant keywords in user generated content can estimate daily rainfall rates of different regions in Sweden using microblog data.

    Microblog data are collected using a microblog crawler. Properties of the data and data collection methods are both discussed extensively. In this thesis three different model types are studied for regression, linear and nonlinear parametric models as well as a nonparametric Gaussian process model. Using cross-validation and optimization the relevant parameters of each model are estimated and the model is evaluated on independent test data. All three models show promising results for nowcasting rainfall rates.

  • 3827.
    Andersson Naesseth, Christian
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Vision and Radar Sensor Fusion for Advanced Driver Assistance Systems2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The World Health Organization predicts that by the year 2030, road traffic injuries will be one of the top five leading causes of death. Many of these deaths and injuries can be prevented by driving cars properly equipped with state-of-the-art safety and driver assistance systems. Some examples are auto-brake and auto-collision avoidance which are becoming more and more popular on the market today. A recent study by a Swedish insurance company has shown that on roadswith speeds up to 50 km/h an auto-brake system can reduce personal injuries by up to 64 percent. In fact in an estimated 40 percent of crashes, the auto-brake reduced the effects to the degree that no personal injury was sustained.

    It is imperative that these so called Advanced Driver Assistance Systems, to be really effective, have good situational awareness. It is important that they have adequate information of the vehicle’s immediate surroundings. Where are other cars, pedestrians or motorcycles relative to our own vehicle? How fast are they driving and in which lane? How is our own vehicle driving? Are there objects in the way of our own vehicle’s intended path? These and many more questions can be answered by a properly designed system for situational awareness.

    In this thesis we design and evaluate, both quantitatively and qualitatively, sensor fusion algorithms for multi-target tracking. We use a combination of camera and radar information to perform fusion and find relevant objects in a cluttered environment. The combination of these two sensors is very interesting because of their complementary attributes. The radar system has high range resolution but poor bearing resolution. The camera system on the other hand has a very high bearing resolution. This is very promising, with the potential to substantially increase the accuracy of the tracking system compared to just using one of the two. We have also designed algorithms for path prediction and a first threat awareness logic which are both qualitively evaluated.

  • 3828.
    Andersson Naesseth, Christian
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Linderman, Scott
    Columbia University, New York City, New York, United States.
    Ranganath, Rajesh
    New York University, New York City, New York, United States.
    Blei, David
    Columbia University, New York City, New York, United States.
    Variational Sequential Monte Carlo2018In: Proceedings of the Twenty-First International Conference on Artificial Intelligence and Statistics, 2018Conference paper (Refereed)
    Abstract [en]

    Many recent advances in large scale probabilistic inference rely on variational methods. The success of variational approaches depends on (i) formulating a flexible parametric family of distributions, and (ii) optimizing the parameters to find the member of this family that most closely approximates the exact posterior. In this paper we present a new approximating family of distributions, the variational sequential Monte Carlo (VSMC) family, and show how to optimize it in variational inference. VSMC melds variational inference (VI) and sequential Monte Carlo (SMC), providing practitioners with flexible, accurate, and powerful Bayesian inference. The VSMC family is a variational family that can approximate the posterior arbitrarily well, while still allowing for efficient optimization of its parameters. We demonstrate its utility on state space models, stochastic volatility models for financial data, and deep Markov models of brain neural circuits.

  • 3829.
    Andersson Naesseth, Christian
    et al.
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning. Linköping University, Faculty of Science & Engineering.
    Lindsten, Fredrik
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning. Linköping University, Faculty of Science & Engineering.
    Schon, Thomas B.
    Uppsala Univ, Sweden.
    High-Dimensional Filtering Using Nested Sequential Monte Carlo2019In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 67, no 16, p. 4177-4188Article in journal (Refereed)
    Abstract [en]

    Sequential Monte Carlo (SMC) methods comprise one of the most successful approaches to approximate Bayesian filtering. However, SMC without a good proposal distribution can perform poorly, in particular in high dimensions. We propose nested sequential Monte Carlo, a methodology that generalizes the SMC framework by requiring only approximate, properly weighted, samples from the SMC proposal distribution, while still resulting in a correctSMCalgorithm. This way, we can compute an "exact approximation" of, e. g., the locally optimal proposal, and extend the class of models forwhichwe can perform efficient inference using SMC. We showimproved accuracy over other state-of-the-art methods on several spatio-temporal state-space models.

  • 3830.
    Andersson Naesseth, Christian
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Lindsten, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Schön, Thomas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Capacity estimation of two-dimensional channels using Sequential Monte Carlo2014In: 2014 IEEE Information Theory Workshop, 2014, p. 431-435Conference paper (Refereed)
    Abstract [en]

    We derive a new Sequential-Monte-Carlo-based algorithm to estimate the capacity of two-dimensional channel models. The focus is on computing the noiseless capacity of the 2-D (1, ∞) run-length limited constrained channel, but the underlying idea is generally applicable. The proposed algorithm is profiled against a state-of-the-art method, yielding more than an order of magnitude improvement in estimation accuracy for a given computation time.

  • 3831.
    Andersson Naesseth, Christian
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Lindsten, Fredrik
    The University of Cambridge, Cambridge, United Kingdom.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Nested Sequential Monte Carlo Methods2015In: Proceedings of The 32nd International Conference on Machine Learning / [ed] Francis Bach, David Blei, Journal of Machine Learning Research (Online) , 2015, Vol. 37, p. 1292-1301Conference paper (Refereed)
    Abstract [en]

    We propose nested sequential Monte Carlo (NSMC), a methodology to sample from sequences of probability distributions, even where the random variables are high-dimensional. NSMC generalises the SMC framework by requiring only approximate, properly weighted, samples from the SMC proposal distribution, while still resulting in a correct SMC algorithm. Furthermore, NSMC can in itself be used to produce such properly weighted samples. Consequently, one NSMC sampler can be used to construct an efficient high-dimensional proposal distribution for another NSMC sampler, and this nesting of the algorithm can be done to an arbitrary degree. This allows us to consider complex and high-dimensional models using SMC. We show results that motivate the efficacy of our approach on several filtering problems with dimensions in the order of 100 to 1 000.

  • 3832.
    Andersson Naesseth, Christian
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Lindsten, Fredrik
    University of Cambridge, Cambridge, UK.
    Schön, Thomas
    Uppsala University, Uppsala, Sweden.
    Sequential Monte Carlo for Graphical Models2014In: Advances in Neural Information Processing Systems, 2014, p. 1862-1870Conference paper (Refereed)
    Abstract [en]

    We propose a new framework for how to use sequential Monte Carlo (SMC) algorithms for inference in probabilistic graphical models (PGM). Via a sequential decomposition of the PGM we find a sequence of auxiliary distributions defined on a monotonically increasing sequence of probability spaces. By targeting these auxiliary distributions using SMC we are able to approximate the full joint distribution defined by the PGM. One of the key merits of the SMC sampler is that it provides an unbiased estimate of the partition function of the model. We also show how it can be used within a particle Markov chain Monte Carlo framework in order to construct high-dimensional block-sampling algorithms for general PGMs.

  • 3833.
    Andersson Naesseth, Christian
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering. Columbia University, USA.
    Ruiz, Francisco
    Columbia University, USA, University of Cambridge, UK.
    Linderman, Scott
    Columbia University, USA.
    Blei, David
    Columbia University, USA.
    Reparameterization Gradients through Acceptance-Rejection Sampling Algorithms2017In: Proceedings of the 20th International Conference on Artificial Intelligence and Statistics, 2017Conference paper (Refereed)
    Abstract [en]

    Variational inference using the reparameterization trick has enabled large-scale approximate Bayesian inference in complex probabilistic models, leveraging stochastic optimization to sidestep intractable expectations. The reparameterization trick is applicable when we can simulate a random variable by applying a differentiable deterministic function on an auxiliary random variable whose distribution is fixed. For many distributions of interest (such as the gamma or Dirichlet), simulation of random variables relies on acceptance-rejection sampling. The discontinuity introduced by the accept-reject step means that standard reparameterization tricks are not applicable. We propose a new method that lets us leverage reparameterization gradients even when variables are outputs of a acceptance-rejection sampling algorithm. Our approach enables reparameterization on a larger class of variational distributions. In several studies of real and synthetic data, we show that the variance of the estimator of the gradient is significantly lower than other state-of-the-art methods. This leads to faster convergence of stochastic gradient variational inference.

  • 3834.
    Andersson, Natasja
    Linköping University, Department of Physics, Chemistry and Biology.
    Personlighetsvariationer hos mjölkkor2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study was to investigate if different personality dimensions existed in dairy cows of two breeds (SRB and Holstein) and if these personality dimensions differed between breed, age and how the animals were placed in the loose housing system. To investigate behavioural consistency, the cows were observed in three different situations: uninterrupted in their home pen, during milking and with a novel object in their home pen. Normal and social behaviour was observed as well as stepping and kicking during milking and interactions with the novel object. Twelve behavioural variables were used in a principal component analysis, which showed two components that together explained 51,2 % of the total variance. The first component reflected aggression and extraversion, which are included in agreeableness and extraversion in the human five-factor model. The second component reflected fear and introversion, which are included in neuroticism and extraversion in the same model. Independent-samples T test showed no significant differences between any of the components and breed or placement in the loose housing system p>0,05, however there was a tendency between the first component and age, where the older group showed a more defined personality p<0,1. Other studies have showed that personality dimensions such as agreeableness, neuroticism and extraversion often exist in several species. Different personalities cope with stressful situations in different ways, making this topic relevant to the improvement of animal welfare.

  • 3835.
    Andersson, Niclas
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, PELAB - Programming Environment Laboratory. Linköping University, The Institute of Technology.
    Comparative Evaluation and Industrial Application of Code Generator Generators1992Conference paper (Other academic)
    Abstract [en]

    The past ten to fifteen years has seen active research in the area of automatically generating the code generator part of compilers from formal specifications. However, less work has been done on evaluating and applying these systems in an industrial setting. This paper attempts to fill this gap.Three systems for automatic generation of code generators are evaluated in this paper: CGSS, BEG and TWIG. CGSS is an older Graham-Glanville style system based on pattern matching through parsing, whereas BEG and TWIG are more recent systems based on tree pattern matching combined with dynamic programming. An industrial-strength code generator previously implemented for a special-purpose language using the CGSS system is described and compared in some detail to our new implementation based on the BEG system. Several problems of integrating local and global register allocation within automatically generated code generators are described, and some solutions proposed. We finally conclude that current technology of automatically generating code generators is viable in an industrial setting. However, further research needs to be done on the problem of properly integrating register allocation with instruction selection, when both are generated from declarative specifications.

  • 3836.
    Andersson, Niclas
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, PELAB - Programming Environment Laboratory. Linköping University, The Institute of Technology.
    Generating Parallel Code from Object Oriented Mathematical Models1995In: PPOPP 1995, 1995, p. 48-57Conference paper (Refereed)
    Abstract [en]

    For a long time efficient use of parallel computers has been hindered by dependencies introduced in software through low-level implementation practice. In this paper we present a programming environment and language called Object-Math (Object oriented Mathematical language for scientific computing), which aims at eliminating this problem by allowing the user to represent mathematical equation-based models directly in the system. The system performs analysis of mathematical models to extract parallelism and automatically generates parallel code for numerical solution.In the context of industrial applications in mechanical analysis, we have so far primarily explored generation of parallel code for solving systems of ordinary differential equations (ODEs), in addition to preliminary work on generating code for solving partial differential equations. Two approaches to extracting parallelism have been implemented and evaluated: extracting parallelism at the equation system level and at the single equation level, respectively. We found that for several applications the corresponding systems of equations do not partition well into subsystems. This means that the equation system level approach is of restricted general applicability. Thus, we focused on the equation-level approach which yielded significant parallelism for ODE systems solution. For the bearing simulation applications we present here, the achieved speedup is however critically dependent on low communication latency of the parallel computer.

  • 3837.
    Andersson, Niclas
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, PELAB - Programming Environment Laboratory. Linköping University, The Institute of Technology.
    Object Oriented Mathematical Modelling and Compilation to Parallel Code1997In: Parallel Computing in Optimization / [ed] Athanasios Migdalas, Panos M. Pardalos and Sverre Storøy, Kluwer Academic Publishers, 1997Chapter in book (Other academic)
    Abstract [en]

    The current state of the art in programming for scientific computing is still rather low-level. The mathematical model behind a computing application usually is written using pen and paper, whereas the corresponding numerical software often is developed manually in Fortran or C. This is especially true in application areas such as mechanical analysis, where complex non-linear problems are the norm, and high performance is required. Ideally, a high-level programming environment would provide computer support for these development steps. This motivated the development of the ObjectMath system. Using ObjectMath, complex mathematical models may be structured in an object oriented way, symbolically simplified, and transformed to efficient numerical code in C++ or Fortran.

    However, many scientific computing problems are quite computationally demanding, which makes it desirable to use parallel computers. Unfortunately, generating parallel code from arbitrary mathematical models is an intractable problem. Therefore, we have focused most of our efforts on a specific problem domain where the main computation is to solve ordinary differential equation systems where most of the computing time is spent in application specific code, rather than in the serial solver kernel. We have investigated automatic parallelisation of the computation of ordinary differential equation systems at three different levels of granularity: the equation system level, the equation level, and the clustered task level. At the clustered task level we employ domain specific knowledge and existing scheduling and clustering algorithms to partition and distribute the computation.

  • 3838.
    Andersson, Niclas
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Overview and industrial application of code generator generators1996In: Journal of Systems and Software, ISSN 0164-1212, E-ISSN 1873-1228, Vol. 32, no 3, p. 185-214Article in journal (Refereed)
    Abstract [en]

    During the past 10 to 15 years, there has been active research in the area of automatically generating the code generator part of compilers from formal specifications. However, little has been reported on the application of these systems in an industrial setting. This paper attempts to fill this gap, in addition to providing a tutorial overview of the most well-known methods. Four systems for automatic generation of code generators are described in this paper. CGSS, BEG, TWIG and BURG. CGSS is an older Graham-Glanville style system based on pattern matching through parsing, whereas BEG, TWIG, and BURG are more recent systems based on tree pattern matching combined with dynamic programming. An industrial-strength code generator previously implemented for a special-purpose language using the CGSS system is described and compared in some detail to our new implementation based on the BEG system. Several problems of integrating local and global register allocations within automatically generated code generators are described, and some solutions are proposed. In addition, the specification of a full code generator for SUN SPARC with register windows using the BEG system is described. We finally conclude that current technology of automatically generating code generators is viable in an industrial setting. However, further research needs to be done on the problem of properly integrating register allocation and instruction scheduling with instruction selection, when both are generated from declarative specifications.

  • 3839.
    Andersson, Niklas
    Linköping University, Department of Thematic Studies, Environmental Science.
    Att hantera sopor i Ringdansen: En studie av hushållens perspektiv2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Ringdansens bostadsområde som är del av Hyresbostäder i Norrköping miljöanpassades under slutet av 1990-talet. Sopstationer med fraktioner för olika avfall infördes. För många hushåll har detta system inneburit problem. Hyresbostäder vill försöka åtgärdaproblemen genom att göra bättre och tydligare information i soprummen.

    Genom intervjustudier undersöks hushållens önskemål och klagomål på det nuvarande systemet, den egna hanteringen av sopor samt motivationen bakom deras handlande. Resultaten visar atthushållen efterfrågar bättre och tydligare information. Vissa av soprummen upplevs som skräpiga och ofräscha. Hushållen sorterar mestadels av pliktkänsla samt av ekonomiska och miljömässiga orsaker.

  • 3840.
    Andersson, Niklas
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Design of Integrated Building Blocks for the Digital/Analog Interface2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The integrated circuit has, since it was invented in the late 1950's, undergone a tremendous development and is today found in virtually all electric equipment. The small feature size and low production cost have made it possible to implement electronics in everyday objects ranging from computers and mobile phones to smart prize tags. Integrated circuits are typically used for data communication, signal processing and data storage. Data is usually stored in digital format but signal processing can be performed both in the digital and in the analog domain. For best performance, the right partition of signal processing between the analog and digital domain must be used. This is made possible by data converters converting data between the domains. A device converting an analog signal into a digital representation is called an analog-to-digital converter (ADC) and a device converting digital data into an analog representation is called a digital-to-analog converter (DAC). In this work we present research results on these data converters and the results are compiled in three different categories. The first contribution is an error correction technique for DACs called dynamic element matching, the second contribution is a power efficient time-to-digital converter architecture and the third is a design methodology for frequency synthesis using digital oscillators.

    The accuracy of a data converter, i.e., how accurate data is converted, is often limited by manufacturing errors. One type of error is the so-called matching error and in this work we investigate an error correction technique for DACs called dynamic element matching (DEM). If distortion is limiting the performance of a DAC, the DEM technique increases the accuracy of the DAC by transforming the matching error from being signal dependent, which results in distortion, to become signal independent noise. This noise can then be spectrally shaped or filtered out and hereby increasing the overall resolution of the system. The DEM technique is investigated theoretically and the theory is supported by measurement results from an implemented 14-bit DAC using DEM. From the investigation it is concluded that DEM increases the performance of the DAC when matching errors are dominating but has less effect at conversion speeds when dynamic errors dominate.

    The next contribution is a new time-to-digital converter (TDC) architecture. A TDC is effectively an ADC converting a time difference into a digital representation. The proposed architecture allows for smaller and more power efficient data conversion than previously reported and the implemented TDC prototype is smaller and more power efficient as compared to previously published TDCs in the same performance segment.

    The third contribution is a design methodology for frequency synthesis using digital oscillators. Digital oscillators generate a sinusoidal output using recursive algorithms. We show that the performance of digital oscillators, in terms of amplitude and frequency stability, to a large extent depends on the start conditions of the oscillators. Further we show that by selecting the proper start condition an oscillator can be forced to repeat the same output sequence over and over again, hence we have a locked oscillator. If the oscillator is locked there is no drift in amplitude or frequency which are common problems for recursive oscillators not using this approach. To find the optimal start conditions a search algorithm has been developed which has been thoroughly tested in simulations. The digital oscillator output is used for test signal generation for a DAC or used to generate tones with high spectral purity using DACs.

    List of papers
    1. A comparison of dynamic element matching in DACs
    Open this publication in new window or tab >>A comparison of dynamic element matching in DACs
    1999 (English)In: Proceedings '99 : Oslo, Norway, 8-9 November 1999 / [ed] Trond Sæther, 1999, p. 385-390Conference paper, Published paper (Other academic)
    Abstract [en]

    In the field of dynamic element matching, DEM, techniques, some "new" important theoretical results have been presented during the last decade. However, no comparison between these different DEM techniques (FRDEM, PRDEM, NSDEM) used in wideband digital-to-analog converters, DACs, has been reported. A brief review of different DEM techniques and a comparison between their properties in terms of complexity, etc., are presented in this paper together with simulation results showing the impact of using different DEM techniques.

    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-112582 (URN)8798263722 (ISBN)
    Conference
    The 17th NORCHIP Conference, November 8-9, Oslo, Norway
    Available from: 2014-12-04 Created: 2014-12-04 Last updated: 2018-11-08Bibliographically approved
    2. A strategy for implementing dynamic element matching in current-steering DACs
    Open this publication in new window or tab >>A strategy for implementing dynamic element matching in current-steering DACs
    2000 (English)In: Mixed-Signal Design, 2000. SSMSD. 2000 Southwest Symposium on, IEEE , 2000, p. 51-56Conference paper, Published paper (Other academic)
    Abstract [en]

    Interesting comparisons of dynamic element matching (DEM) techniques, have been presented during the last decade. However, not many chip implementations of these DEM techniques have been presented so far. A brief review of different DEM techniques are presented in this paper together with a strategy for implementing the partial randomization DEM, PRDEM, technique in a 3.3 V supply, 14 bit CMOS current-steering wideband digital-to-analog converter (DAC)

    Place, publisher, year, edition, pages
    IEEE, 2000
    Keywords
    0.35 micron;11 MHz;14 bit;3.3 V;88 MHz;CMOS wideband DAC;current-steering DACs;dynamic element matching;partial randomization technique;wideband digital-to-analog converter;CMOS integrated circuits;digital-analogue conversion;
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-70637 (URN)10.1109/SSMSD.2000.836445 (DOI)0-7803-5975-5 (ISBN)
    Conference
    SSMSD 2000, 27 - 29 Feb. 2000, San Diego, CA , USA
    Available from: 2011-09-14 Created: 2011-09-14 Last updated: 2018-11-08
    3. Models and Implementation of a Dynamic Element Matching DAC
    Open this publication in new window or tab >>Models and Implementation of a Dynamic Element Matching DAC
    2003 (English)In: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 34, no 1, p. 7-16Article in journal (Refereed) Published
    Abstract [en]

    The dynamic element matching (DEM) techniques for digital-to-analog converters (DACs) has been suggested as a promising method to improve matching between the DAC''s reference levels. However, no work has so far taken the dynamic effects that limit the performance for higher frequenciesinto account. In this paper we present a model describing the dynamic properties of a DEM DAC and compare the simulated results with measurements of a 14-bit current-steering DEM DAC implemented in a 0.35-μm CMOS process. The measured data agrees well with the results predicted by the used model. It is also shown that the DEM technique does not necessarily increase the performance of a DAC when dynamic errors are dominating the achievable performance.

    Place, publisher, year, edition, pages
    Netherlands: Springer, 2003
    Keywords
    DAC, DEM, CMOS, matching, current-steering
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-21845 (URN)10.1023/A:1020331415597 (DOI)
    Available from: 2009-10-06 Created: 2009-10-06 Last updated: 2017-12-13
    4. A Vernier Time-to-Digital Converter With Delay Latch Chain Architecture
    Open this publication in new window or tab >>A Vernier Time-to-Digital Converter With Delay Latch Chain Architecture
    2014 (English)In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 61, no 10, p. 773-777Article in journal (Refereed) Published
    Abstract [en]

    A new Vernier time-to-digital converter (TDC) architecture using a delay line and a chain of delay latches is proposed. The delay latches replace the functionality of one delay chain and the sample register commonly found in Vernier converters, hereby enabling power and hardware efficiency improvements. The delay latches can be implemented using either standard or full custom cells, allowing the architecture to be implemented in field-programmable gate arrays, digital synthesized application-specific integrated circuits, or in full custom design flows. To demonstrate the proposed concept, a 7-bit Vernier TDC has been implemented in a standard 65-nm CMOS process with an active core size of 33 mu m x 120 mu m. The time resolution is 5.7 ps with a power consumption of 1.75 mW measured at a conversion rate of 100 MS/s.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2014
    Keywords
    CMOS; delay latch; time-to-digital converter (TDC); Vernier
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-112180 (URN)10.1109/TCSII.2014.2345289 (DOI)000343320500009 ()
    Available from: 2014-11-18 Created: 2014-11-18 Last updated: 2017-12-05
    5. Power-efficient time-to-digital converter for all-digital frequency locked loops
    Open this publication in new window or tab >>Power-efficient time-to-digital converter for all-digital frequency locked loops
    2015 (English)In: 2015 EUROPEAN CONFERENCE ON CIRCUIT THEORY AND DESIGN (ECCTD), Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 300-303Conference paper, Published paper (Refereed)
    Abstract [en]

    An 8-bit time-to-digital converter (TDC) for all-digital frequency-locked loops ispresented. The selected architecture uses a Vernier delay line where the commonlyused D flip-flops are replaced with a single enable transistor in the delay elements.This architecture allows for an area efficient and power efficient implementation. Thetarget application for the TDC is an all-digital frequency-locked loop which is alsooverviewed in the paper. A prototype chip has been implemented in a 65 nm CMOSprocess with an active core area of 75μmˆ120μm. The time resolution is 5.7 ps with apower consumption of 1.85 mW measured at 50 MHz sampling frequency.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2015
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-112589 (URN)10.1109/ECCTD.2015.7300008 (DOI)000380498200010 ()978-1-4799-9877-7 (ISBN)
    Conference
    European Conference on Circuit Theory and Design (ECCTD)
    Available from: 2014-12-04 Created: 2014-12-04 Last updated: 2019-01-07Bibliographically approved
    6. Steady-state cycles in digital oscillators
    Open this publication in new window or tab >>Steady-state cycles in digital oscillators
    2014 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Digital recursive oscillators locked in steady-state can be used to generate sinusoids with high spectral purity. The locking occurs when the oscillator returns to a previously visited state and repeats its sequence. In this work we propose a new search algorithm and two new search strategies to find all steady-states for a given oscillator configuration. The improvement in spurious-free dynamic range is between 7 and 40 dB compared to previously reported results. The algorithm is also able to find oscillator sequences for more frequencies than previously reported work. A key part of the method is the reduction of the search space made possible by a proposed extension of existing theory on recursive oscillators. Specific properties of digital oscillators in a steady-state are also discussed. It is shown that the initial states can be used to individually control the phase, amplitude, spectral purity, and also cycle length of the oscillator output.

    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-112590 (URN)
    Available from: 2014-12-04 Created: 2014-12-04 Last updated: 2018-11-08Bibliographically approved
  • 3841.
    Andersson, Niklas
    Linköping University, Department of Management and Engineering.
    Gesällprovets tillverkningsprocess2008Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Examensarbetet är en beskrivande rapport om tillverkningsprocessen av ett gesällprov. Rapportens syfte är att beakta olika konstruktioner och hur de förvärvade kunskaperna används för att utföra en slutprodukt, i det här fallet ett gesällprov. Rapporten försöker svara på vilka faktorer som varit mest avgörande för ett lyckat resultat.

    Tyngdpunkten i arbetet ligger i att beskriva tillverkningsprocessen. Rapporten beskriver resonemanget kring valet av en möbel. Den presenterar olika träslag och hur de kan påverka möbelns uttryck. Vidare berättar rapporten om olika alternativ på skivmaterial att använda som blindträ. Uttag och hantering av faner och massivträ förklaras. Rapporten visar även olika konstruktioner och sammansättningar.

    I den avslutande delen presenteras resultatet av tillverkningen och granskarnas betygssättning. Ett resonemang förs angående vilka faktorer, så som erfarenheter, förvärvade kunskaper, noggrannhet etc. som påverkat resultatet. Slutligen beskrivs olika svårigheter och vad som skulle kunna göras annorlunda.

  • 3842.
    Andersson, Niklas
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Växelväljare i stadsbuss2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The gear selector presently used has a large build-in depth which causes trouble at integration in dashboard and the light bulbs for indication light has short life length. The development of distributed systems has opened the possibility for Scania to use a gear selector of their own and therefore it’s in Scanias interest to examine the option.

    The concept presented in this degree thesis is a very compact unit, the build-in depth is only a fourth of the gear selector used presently. The pushbuttons are rubber which are illuminated from underneath. For indication indication- and backlight OSRAMs HYPER T66 is used.

    This is a package containing three, from each other independent, LEDs. A microcontroller, Microchip PIC18F248, reads the pushbuttons, communicates with the gearbox’s control unit (via CAN, protocol SAE-J1939) and drives the LEDs. With a gear selector that uses CAN-technology and LED’s instead of light bulbs and rubber pushbuttons in place of common switches a unit without need of maintenance is received. Furthermore, the Scania brand increases because the gear selector’s performance can be shaped due to the needs and simultaneously improve functionality. Quality control is another important advantage. The design allows little build-in depth which is of great importance since the present gear selector can’t be placed where desired due to its large depth.

    One problem with the CAN-systems protocol, SAE-J1939l, is that only D, N and R are supported. This means that Scania should wait until the protocol is ready if it’s necessary with more gears than D, N and R.

  • 3843.
    Andersson, Niklas
    et al.
    Ericsson Microelectronics AB.
    Andersson, Ola
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Vesterbacka, Mark
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Wikner, Jacob
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Models and Implementation of a Dynamic Element Matching DAC2003In: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 34, no 1, p. 7-16Article in journal (Refereed)
    Abstract [en]

    The dynamic element matching (DEM) techniques for digital-to-analog converters (DACs) has been suggested as a promising method to improve matching between the DAC''s reference levels. However, no work has so far taken the dynamic effects that limit the performance for higher frequenciesinto account. In this paper we present a model describing the dynamic properties of a DEM DAC and compare the simulated results with measurements of a 14-bit current-steering DEM DAC implemented in a 0.35-μm CMOS process. The measured data agrees well with the results predicted by the used model. It is also shown that the DEM technique does not necessarily increase the performance of a DAC when dynamic errors are dominating the achievable performance.

  • 3844.
    Andersson, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Statistics.
    Hansson, Josef
    Linköping University, Department of Computer and Information Science, Statistics.
    Metodik för detektering av vägåtgärder via tillståndsdata2010Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Swedish Transport Administration has, and manages, a database containing information of the status of road condition on all paved and governmental operated Swedish roads. The purpose of the database is to support the Pavement Management System (PMS). The PMS is used to identify sections of roads where there is a need for treatment, how to allocate resources and to get a general picture of the state of the road network condition. All major treatments should be reported which has not always been done.

    The road condition is measured using a number of indicators on e.g. the roads unevenness. Rut depth is an indicator of the roads transverse unevenness. When a treatment has been done the condition drastically changes, which is also reflected by these indicators.

    The purpose of this master thesis is to; by using existing indicators make predictions to find points in time when a road has been treated.

    We have created a SAS-program based on simple linear regression to analyze rut depth changes over time. The function of the program is to find levels changes in the rut depth trend. A drastic negative change means that a treatment has been made.

    The proportion of roads with an alleged date for the latest treatment earlier than the programs latest detected date was 37 percent. It turned out that there are differences in the proportions of possible treatments found by the software and actually reported roads between different regions. The regions North and Central have the highest proportion of differences. There are also differences between the road groups with various amount of traffic. The differences between the regions do not depend entirely on the fact that the proportion of heavily trafficked roads is greater for some regions.

  • 3845.
    Andersson, Niklas
    et al.
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, The Institute of Technology.
    Vesterbacka, Mark
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, The Institute of Technology.
    A Vernier Time-to-Digital Converter With Delay Latch Chain Architecture2014In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 61, no 10, p. 773-777Article in journal (Refereed)
    Abstract [en]

    A new Vernier time-to-digital converter (TDC) architecture using a delay line and a chain of delay latches is proposed. The delay latches replace the functionality of one delay chain and the sample register commonly found in Vernier converters, hereby enabling power and hardware efficiency improvements. The delay latches can be implemented using either standard or full custom cells, allowing the architecture to be implemented in field-programmable gate arrays, digital synthesized application-specific integrated circuits, or in full custom design flows. To demonstrate the proposed concept, a 7-bit Vernier TDC has been implemented in a standard 65-nm CMOS process with an active core size of 33 mu m x 120 mu m. The time resolution is 5.7 ps with a power consumption of 1.75 mW measured at a conversion rate of 100 MS/s.

  • 3846.
    Andersson, Niklas
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Vesterbacka, Mark
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Power-efficient time-to-digital converter for all-digital frequency locked loops2015In: 2015 EUROPEAN CONFERENCE ON CIRCUIT THEORY AND DESIGN (ECCTD), Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 300-303Conference paper (Refereed)
    Abstract [en]

    An 8-bit time-to-digital converter (TDC) for all-digital frequency-locked loops ispresented. The selected architecture uses a Vernier delay line where the commonlyused D flip-flops are replaced with a single enable transistor in the delay elements.This architecture allows for an area efficient and power efficient implementation. Thetarget application for the TDC is an all-digital frequency-locked loop which is alsooverviewed in the paper. A prototype chip has been implemented in a 65 nm CMOSprocess with an active core area of 75μmˆ120μm. The time resolution is 5.7 ps with apower consumption of 1.85 mW measured at 50 MHz sampling frequency.

  • 3847.
    Andersson, Niklas
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Vesterbacka, Mark
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Gustafsson, Oskar
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, The Institute of Technology.
    Wikner, Jacob
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Steady-state cycles in digital oscillators2014Manuscript (preprint) (Other academic)
    Abstract [en]

    Digital recursive oscillators locked in steady-state can be used to generate sinusoids with high spectral purity. The locking occurs when the oscillator returns to a previously visited state and repeats its sequence. In this work we propose a new search algorithm and two new search strategies to find all steady-states for a given oscillator configuration. The improvement in spurious-free dynamic range is between 7 and 40 dB compared to previously reported results. The algorithm is also able to find oscillator sequences for more frequencies than previously reported work. A key part of the method is the reduction of the search space made possible by a proposed extension of existing theory on recursive oscillators. Specific properties of digital oscillators in a steady-state are also discussed. It is shown that the initial states can be used to individually control the phase, amplitude, spectral purity, and also cycle length of the oscillator output.

  • 3848.
    Andersson, Niklas
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System.
    Vesterbacka, Mark
    Linköping University, Department of Electrical Engineering, Electronics System.
    Wikner, Jacob
    Linköping University, Department of Electrical Engineering, Electronics System.
    Rudberg, Mikael
    Linköping University, Department of Electrical Engineering, Electronics System.
    Improvement of segmented DACs (Swedish pat. 0001917-4)2000Patent (Other (popular science, discussion, etc.))
  • 3849.
    Andersson, Niklas
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Wikner, Jacob
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A comparison of dynamic element matching in DACs1999In: Proceedings '99 : Oslo, Norway, 8-9 November 1999 / [ed] Trond Sæther, 1999, p. 385-390Conference paper (Other academic)
    Abstract [en]

    In the field of dynamic element matching, DEM, techniques, some "new" important theoretical results have been presented during the last decade. However, no comparison between these different DEM techniques (FRDEM, PRDEM, NSDEM) used in wideband digital-to-analog converters, DACs, has been reported. A brief review of different DEM techniques and a comparison between their properties in terms of complexity, etc., are presented in this paper together with simulation results showing the impact of using different DEM techniques.

  • 3850.
    Andersson, Niklas
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Wikner, Jacob
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A strategy for implementing dynamic element matching in current-steering DACs2000In: Mixed-Signal Design, 2000. SSMSD. 2000 Southwest Symposium on, IEEE , 2000, p. 51-56Conference paper (Other academic)
    Abstract [en]

    Interesting comparisons of dynamic element matching (DEM) techniques, have been presented during the last decade. However, not many chip implementations of these DEM techniques have been presented so far. A brief review of different DEM techniques are presented in this paper together with a strategy for implementing the partial randomization DEM, PRDEM, technique in a 3.3 V supply, 14 bit CMOS current-steering wideband digital-to-analog converter (DAC)

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