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  • 20901. Örnemark, U
    et al.
    Lundgren, B
    Langer, S
    Metrologi: ett nygammalt verktyg i kemistens kvalitetssäkringsarbete1998In: Ytforum / Sveriges galvanotekniska förening, ISSN 0349-4470, Vol. 31, no 4Article in journal (Other academic)
  • 20902.
    Örnemark, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Bridging cultural gaps in quality assurance2001In: Accreditation and Quality Assurance, ISSN 0949-1775, E-ISSN 1432-0517, Vol. 6, no 5, p. 138-139Article in journal (Other academic)
  • 20903.
    Örnemark, Ulf
    SP – Sveriges Provnings- och Forskningsinstitut.
    Evaluation of a model for participation in proficiency testing schemes proposed in Nordtest project 1421-981999Report (Refereed)
  • 20904.
    Örnemark, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Have uncertainty statements improved over the last ten years? Experience from the IRMM-international measurement evaluation programme (IMEP)1999Conference paper (Other academic)
  • 20905.
    Örnemark, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    IMEP 7 - Trace elements in human serum1999In: CITAC newsletter, no Febr, p. 9-10Article in journal (Other academic)
  • 20906.
    Örnemark, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Interlaboratory comparisons in support of international comparability and traceability for clinical chemical measurements1999In: EQA news, ISSN 0906-0588, Vol. 10, no 3, p. 63-Article in journal (Other academic)
  • 20907.
    Örnemark, Ulf
    SP – Sveriges Provnings- och Forskningsinstitut.
    Metrology in chemistry - Enquiry concerning the current situation and future needs in Sweden conducted for the Regular Committee of the SMT-programme.1998Report (Refereed)
  • 20908.
    Örnemark, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Proficiency testing in analytical chemistry, microbiology and laboratory medicine: Working group discussions on current status, problems and future directions2001In: Accreditation and Quality Assurance, ISSN 0949-1775, E-ISSN 1432-0517, Vol. 6, no 5, p. 140-146Article in journal (Other academic)
  • 20909.
    Örnemark, Ulf
    SP – Sveriges Provnings- och Forskningsinstitut.
    Provning av vidhäftning hos keramiska våtrumskonstruktioner efter olika härdningsbetingelser1999Report (Refereed)
  • 20910.
    Örnemark, Ulf
    SP – Sveriges Provnings- och Forskningsinstitut.
    Sammanställning av resultat från svenska deltagare i provningsjämförelsen IMEP-91999Report (Refereed)
  • 20911. Örnemark, Ulf
    The International Measurement Evaluation Programme (IMEP) IMEP-6 Trace elements in water1999In: Accreditation and Quality Assurance, ISSN 0949-1775, E-ISSN 1432-0517, Vol. 3, no 2, p. 56-68Article in journal (Other academic)
  • 20912.
    Örnemark, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    The IRMM International Measurement Evaluation Programme (IMEP) IMEP-7: Inorganic components in human serum1999In: Accreditation and Quality Assurance, ISSN 0949-1775, E-ISSN 1432-0517, Vol. 4, no 11, p. 463-472Article in journal (Other academic)
  • 20913.
    Örnemark, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    The IRMM-International Measurement Evaluation Programme- IMEP-7, Inorganic components in human serum. Report to the Slovak participants1999Conference paper (Other academic)
  • 20914.
    Örnemark, Ulf
    SP – Sveriges Provnings- och Forskningsinstitut.
    TQM på laboratoriet - introduktion till kvalitetssäkring av kemiska mätningar2000Report (Refereed)
  • 20915.
    Örnemark, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Utvärdering av mätosäkerhet i kemisk analys. 2: a rev. utg. Översättning och bearbetning från den 22001Report (Refereed)
  • 20916.
    Örnemark, Ulf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Utvärdering av mätosäkerhet i kemisk analys. ERSATT AV SP RAPPORT 2001: 242000Report (Refereed)
  • 20917. Örnemark, Ulf
    et al.
    Holmgren, Magnus
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Measurement uncertainty - Surveys about customers knowledge, reactions and needs2001Report (Refereed)
  • 20918.
    Örtengren, Eva
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Mögelpåväxt i friska hus1988Report (Refereed)
  • 20919.
    Örtqvist, Daniel
    et al.
    Luleå University of Technology, Sweden.
    Liljedahl, Mats
    RISE, Swedish ICT, Interactive Institute.
    Immersion and Gameplay Experience: A Contingency Framework2010In: International Journal of Computer Games Technology, Vol. 2010Article in journal (Refereed)
    Abstract [en]

    The nature of the relationship between immersion and gameplay experience is investigated, focusing primarily on the literature related to flow. In particular, this paper proposes that immersion and gameplay experience are conceptually different, but empirically positively related through mechanisms related to flow. Furthermore, this study examines gamers' characteristics to determine the influence between immersion and gameplay experiences. The study involves 48 observations in one game setting. Regression analyses including tests for moderation and simple slope analysis are used to reveal gamers' age, experience, and understanding of the game, which moderate the relationship between immersion and gameplay experience. The results suggest that immersion is more positive for gameplay experience when the gamer lacks experience and understanding of the game as well as when the gamer is relatively older. Implications and recommendations for future research are discussed at length in the paper.

  • 20920. Östberg, G
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Emulsification of alkyds for industrial coatings1996In: JCT: Journal of Coatings Technology, ISSN 0361-8773, Vol. 68, p. 39-45Article in journal (Refereed)
    Abstract [en]

    Alkyd emulsions have so far mostly been used in consumer paints. These are relatively easy to emulsify due to their low viscosity. Lately alkyd emulsions for industrial paint have gained increasing attention. Alkyd for industrial paints have a much higher viscosity than alkyds for consumer paints which requires other emulsification techniques. In this work an alkyd with 40 % oil length have been emulsified by the inversion technique. Inversion emulsification by adding water to an alkyd/surfactant mixture at constant temperature give emulsions with droplet sizes below 1pm at a concentration of 3 % on the alkyd phase. Small droplets are necessary for colloidal stability of the emulsion. The solubility of surfactant in the alkyd and the water phase determines at which water concentration the emulsion inverts. High molecular weight ethoxylated anionic surfactants are effective as emulsifiers. Using these surfactants the emulsification becomes less dependent on emulsification temperature than when nonionic surfactants are used.

  • 20921. Östberg, G
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Mechanical stability of alkyd emulsions. Part 2: Influence of alkyd properties1994In: JCT: Journal of Coatings Technology, ISSN 0361-8773, Vol. 66, no 838, p. 37-41Article in journal (Refereed)
    Abstract [en]

    The development of water borne alkyd paints based on alkyd emulsions has been stimulated by more stringent health and environment regulations. In addition, alkyd paints may have better performance in some applications compared to other types of water -borne paints such as latex dispersions. One problem that needs to be overcome is the limited colloidal stability of alkyd emulsions. It is important that the emulsions are not destabilized when exposed to shear forces such as those produced by pumps used by the paint industry. An alkyd emulsion consist of alkyd oil droplets dispersed in water and stabilized by a surface active agent (emulsifier). Part 1 of this serie describes the influence of emulsion droplet size and type or concentration of the emulsifier on the shear stability. The present study is an additional investigation of the influence of the alkyd properties on shear stability. Increasing the acid value of the alkyd increases the stability of emulsions stabilized with nonionic emulsifiers. Emulsions made using alkyds with shorter oil lengths and higher viscosities were less stable to shear compared to alkyds with higher oil lengths and lower viscosities.

  • 20922. Östberg, G
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Huldén, M
    YKI – Ytkemiska institutet.
    Influence of emulsifier on the formation of alkyd emulsions1995In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 94, p. 161-171Article in journal (Refereed)
    Abstract [en]

    In traditional alkyd paints, the alkyd is dissolved in an organic solvent such as mineral spirit. For health and environmental reasons there is an increasing interest in water-borne alkyd paints. Alkyd emulsions are therefore an interesting alternative. The alkyd emulsion should have a good colloidal stability at a low concentration of surfactant. A high concentration of surfactant gives undesired properties of the paint film, as for example water sensitivity. In this paper, the influence of emulsification temperature and emulsifier concentration on the formation of alkyd emulsions has been investigated. The temperature dependence observed with both anionic and nonionic emulsifiers is related to the change in viscosity of the alkyd with temperature. In the case of nonionic emulsifiers, an additional effect is seen due to the change in HLB (Hydrophilic Lipophilic Balance) of the surfactant with temperature. A concentration corresponding to a close packing of the non-ionic surfactant on the surface of the droplets is needed to obtain a stable emulsion when nonionic surfactants are used. In the case of anionic emulsifiers, stable emulsions can be obtained at low concentrations giving a very low packing density at the surface.

  • 20923. Östberg, G
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Huldén, M
    YKI – Ytkemiska institutet.
    Mechanical stability of alkyd emulsions. Part 1: Influence of emulsion droplet size and the emulsifier1994In: JCT: Journal of Coatings Technology, ISSN 0361-8773, Vol. 66, no 832, p. 37-46Article in journal (Refereed)
    Abstract [en]

    The limited colloidal stability of alkyd emulsions compared to that of organic solvent-borne alkyd paints is a well known problem. For environmental reasons, however, they have a great advantage since they are water-borne. In this study, we have investigated the influence of emulsifier and initial droplet size on the mechanical stability of alkyd emulsions. Anionic emulsifiers have previously been shown to be more effective than nonionic emulsifiers in the formation of alkyd emulsions. Here it has been found that an anionic emulsifier also gave more stable emulsions at lower concentrations than did the nonionics. Emulsions stabilized with a nonionic emulsifier showed the same stability as the one with the anionic emulsifiers if the concentration was increased. Too high a concentration of surfactants is undesirable in paints, however, since it increases the water sensitivity of the paint film. The mechanical stability of anionically stabilized emulsions was less sensitive to the initial droplet size compared to emulsions stabilized with a nonionic emulsifier.

  • 20924. Östberg, G
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Sörenssen, K
    Distribution of driers between the alkyd and aqueous phase in alkyd emulsions and its relation to drying properties1992In: JCT: Journal of Coatings Technology, ISSN 0361-8773, Vol. 64, no 814, p. 33-43Article in journal (Refereed)
    Abstract [en]

    The influence of pH, emulsifiers and alkyd properties on the distribution of driers between the alkyd- and water phase in alkyd emulsions has been studied. When the pH in the emulsion is decreased, cobalt and calcium driers are redistributed towards the water phase. However, zirconium was found to remain in the alkyd phase independent of pH. Hydrophilic anionic emulsifiers were found to decrease the amount of cobalt and calcium driers in the alkyd phase. The distribution is not influenced by alkyd properties such as oil length or acid values. The relation between the distribution of driers and drying properties has also been investigated. The results indicate a correlation between the early drying rate and cobalt concentration in the alkyd phase.

  • 20925. Östberg, G
    et al.
    Huldén, M
    YKI – Ytkemiska institutet.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Holmberg, K
    YKI – Ytkemiska institutet.
    Alkyd emulsions1994In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 24, p. 281-297Article in journal (Refereed)
    Abstract [en]

    Various aspects of alkyd emulsion technology have been investigated. Firstly, the influence of alkyd oil length, acid value and hydroxyl number, as well as the type of surfactant used as emulsifier, on shear stability of alkyds emulsions have been studied. It was found that the acid value was the most important alkyd parameter, the stability increasing with increasing oil length. It is also shown that anionic surfactants give emulsions with small droplet sizes down at lower concentrations than nonionics. Secondly, polymerizable nonionic surfactants have been tested as emulsifiers and compared with conventional surfactants of the same HLB. It was found that surfactants capable of participating in the autoxidative curing process give faster drying and improved film hardness compared with non-reactive surfactants. Thirdly, the distribution of driers between the alkyd phase and the water phase has been investigated. It was found that low pH and the use of hydrophilic anionic surfactants, such as SDS, favour partitioning of cobalt into the aqueous phase which is unfavourable with respect to drying properties.

  • 20926.
    Östberg, Gunilla
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, Trätek..
    Vattenbaserade vattenavvisande medel för impregnering av trä1991Report (Other academic)
    Abstract [sv]

    En ny typ av vattenbaserade vattenavvisande medel för behandling av trä har studerats. Med två medel baserade på tallharts respektive linolsyra har en vattenavvisande effekt uppnåtts som är bättre än med ett kommersiellt lösningsmedelbaserat medel, som använts som referens. Medlen har också provats med kommersiella fungicider tillsatta och bra vattenavvisande effekt har erhållits vid låga koncentrationer.

  • 20927. Östberg, Joakim
    Stabila bjälklag för säkra våtrum. Innovativ kombination av trä och ÈPSCement. Examensarbete i Byggnadsteknik2006Report (Refereed)
  • 20928.
    Östberg, Kenneth
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Elektronik, Pålitliga system.
    Johansson, Rolf
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Elektronik, Pålitliga system.
    Use of quality metrics for functional safety in systems of cooperative vehicles2012In: LNCS vol. 7613: Computer Safety, Reliability, and Security, 2012, , p. 174-179Conference paper (Refereed)
  • 20929.
    Östberg, Kenneth
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Elektronik, Pålitliga system.
    Törngren, M.
    KTH Royal Institute of Technology, Sweden.
    Asplund, F.
    KTH Royal Institute of Technology, Sweden.
    Bengtsson, M.
    Chalmers University of Technology, Sweden.
    Intelligent transport systems - The role of a safety loop for holistic safety management2014In: Proceedings 33rd Workshop on Computer Safety, Reliability, and Security, Springer International Publishing , 2014, , p. 3-10p. 3-10Conference paper (Refereed)
    Abstract [en]

    An ITS represents a Cyber-Physical System (CPS), which will involve information exchange at operational level as well as potential explicit collaboration between separate entities (systems of systems). Specific emphasis is required to manage the complexity and safety of such future CPS. In this paper we focus on model-based approaches for these purposes for analyzing and managing safety throughout the lifecycle of ITS. We argue that: (1) run-time risk assessment will be necessary for efficient ITS; (2) an information centric approach will be instrumental for future ITS to support all aspects of safety management - a "safety loop"; (3) a formal basis is required to deal with the large amounts of information present in an ITS. We elaborate these arguments and discuss what is required to support their realization.

  • 20930. Österberg, E
    et al.
    Bergström, K
    Holmberg, K
    YKI – Ytkemiska institutet.
    Riggs, JA
    Van Alstine, JM
    Schuman, TP
    Comparison of polysaccharide and poly(ethylene glycol) coatings for reduction of protein adsorption on polystyrene surfaces1993In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 77, p. 159-169Article in journal (Refereed)
    Abstract [en]

    There has been much recent interest in the use of poly(ethylene glycol)s (PEGs) for a variety of biotechnical applications. In the present work we have immobilized several cellulose derivatives and dextran on polystyrene surfaces and have measured the extent of fibrinogen adsorption onto the coated surfaces. Immobilization was achieved by adsorption onto clean polystyrene and by covalent linkage of oxidized polysaccharides to polyethylenimine which was ionically bound to polystyrene. Covalently bound polysaccharides. and adsorbed polysaccharides that are strongly held, compare well with poly(ethylene glycol) in preventing fibrinogen adsorption. The same polymers were coupled to polystyrene latex particles to permit examination by analytical microparticle electrophoresis. This investigation suggests that adsorbed polysaccharides form thicker layers than do covalently bound polysaccharides. Despite the polysaccharides being bound at many points along the polymer chain while PEG is bound only at the polymer terminus, the functional equivalence of polysaccharide and PEG coatings is of significance in interpreting the protein-rejecting ability of polymer-modified surfaces.

  • 20931. Österberg, FW
    et al.
    Dalslet, BT
    Snakenborg, D
    Johansson, Christer
    RISE, Swedish ICT, Acreo.
    Hansen, MF
    Chip-Based Measurements of Brownian Relaxation of Magnetic Beads Using a Planar Hall Effect Magnetic Field Sensor2010In: AIP Conference Proceedings, Vol. 1311, p. 176-182Article in journal (Refereed)
  • 20932.
    Österberg, M
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Interactions between cellulose surfaces: Effect of solution pH2000In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 14, p. 603-618Article in journal (Refereed)
    Abstract [en]

    The forces acting between cellulose surfaces have been studied using the interferometric surface force apparatus. The cellulose surfaces were prepared by Langmuir-Blodgett deposition of trimethylsilyl cellulose (TMSC) onto hydrophobised mica. Prior to measurements the surfaces were desilylated to obtain pure cellulose. The degree of silylation and the molecular weight of the TMSC both affect the structure of the deposited layer. This was observed from the surface pressure/area isotherm, force versus distance curves and atomic force microscopy images. The forces between the cellulose surfaces were found to depend on the pH of the solution. In dilute electrolyte solutions the cellulose film was uncharged and rather compact when the pH of the solution was 6.0. However, when the pH was increased to 7.3 the cellulose film swelled considerably and a long-range steric force was measured. The swelling of the film is interpreted as being due to dissociation of a few carboxylic acid groups present along the cellulose chain. The forces measured were, however, dominated by steric interactions. The repulsion does not increase substantially when the pH is increased from 7.3 to 9.5. Our results suggest that the pKa of the acid groups present within the cellulose film is larger than it would be in bulk aqueous solution.

  • 20933.
    Österberg, M
    et al.
    YKI – Ytkemiska institutet.
    Laine, J
    Stenius, P
    Kumpulainen, A
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Forces between xylan-coated surfaces: Effect of polymer charge density and background electrolyte2001In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 242, p. 59-66Article in journal (Refereed)
  • 20934.
    Östergren, K
    SIK – Institutet för livsmedel och bioteknik.
    FUSIONS definitional frameword for food waste (FP7-rapport)2014Report (Other academic)
  • 20935.
    Östergren, K
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Environment.
    Normann, A
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Flavour.
    Matsvinn och Matavfall2016Report (Other academic)
  • 20936.
    Östergren, Karin
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Productivity - the food industry challenge2010In: Food and Beverage International, Vol. 9, no 3, p. 36-37Article in journal (Refereed)
  • 20937.
    Östergren, Karin
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    REELIV-redskap för effektiv och resurssnål livsmedelsproduktion2012Report (Other academic)
  • 20938.
    Östergren, Karin
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Säker och miljöeffektiv livsmedelslogistik2009Report (Other academic)
  • 20939.
    Östergren, Karin
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Sundström, B
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Berlin, J
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Lorentzon, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Johansson, B
    REELIV - Redskap för effektiv och resurssnål livsmedelsproduktion.2012Report (Other academic)
  • 20940.
    Östergren, Mattias
    RISE - Research Institutes of Sweden, ICT, SICS.
    TCP Performance in Ad Hoc Networks2000Report (Other academic)
    Abstract [en]

    Ad hoc networks are mobile wireless networks which do not have any kind of fixed infrastructure. The routing layer in an ad hoc network ties the network together into a seamless entity and provide transparent services to higher layer protocols. This thesis examines the interactions of two routing protocols, AODV and DSR and how the mobile ad hoc network environment affect TCP performance. The results presented here are as follows: the path length and the presence of competing traffic are the main factors of TCP throughput performance. The size of TCP window affects the loss rate, but the loss rate is not strongly correlated to throughput performance. Using TCP selective acknowledgement option does not improve throughput. Finally, there is hardly any difference in TCP throughput when using DSR and AODV. These conclusions are supported by extensive simulation experiments.

  • 20941.
    Österholm, L-H
    Organisk kemi (Kmo).
    Stenkol: provberedning1986Report (Refereed)
  • 20942.
    Österlind, Fredrik
    RISE - Research Institutes of Sweden, ICT, SICS.
    A Sensor Network Simulator for the Contiki OS2006Report (Other academic)
    Abstract [en]

    This report introduces a new sensor network simulator for the Contiki OS - the COOJA Simulator. The Contiki OS is a portable operating system designed specifically for resource limited devices such as sensor nodes. It is built around an event-driven kernel but supports pre-emptive multithreading at a per-process basis. It also supports a full TCP/IP stack via uIP and the programming abstraction Protothreads. The main design goal of the COOJA Simulator is extendibility, for which Interfaces and Plugins are used. An Interface represents a sensor node property or device, such as a position, a button or a radio transmitter. A Plugin is used to interact with a simulation, for example to control the simulation speed or to watch all network traffic between the simulated nodes. Both new Plugins and Interfaces can easily be created and added to the simulation environment. A number of other parts of the simulator, for example a radio medium responsible for forwarding radio network data, can also be implemented and added to the simulator. And by supporting several different simulation environments at the same time in one simulation, different underlying hardware platforms can be simulated in heterogeneous networks. Java Native Interface is used to connect the new simulator with Contiki, allowing simulated applications to run in a real Contiki system. By using this approach, any simulated application can then be run on a real sensor node unaltered.

  • 20943.
    Österlind, Fredrik
    RISE, Swedish ICT, SICS. Department of Information Technology.
    Improving Low-Power Wireless Protocols with Timing-Accurate Simulation2011Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Low-power wireless technology enables numerous applications in areas from environmental monitoring and smart cities, to healthcare and recycling. But resource-constraints and the distributed nature of applications make low-power wireless networks difficult to develop and understand, resulting in increased development time, poor performance, software bugs, or even network failures. Network simulators offer full non-intrusive visibility and control, and are indispensible tools during development. But simulators do not always adequately represent the real world, limiting their applicability. In this thesis I argue that high simulation timing accuracy is important when developing high-performance low-power wireless protocols. Unlike in generic wireless network simulation, timing becomes important since low-power wireless networks use extremely timing-sensitive software techniques such as radio duty-cycling. I develop the simulation environment Cooja that can simulate low-power wireless networks with high timing accuracy. Using timing-accurate simulation, I design and develop a set of new low-power wireless protocols that improve on throughput, latency, and energy-efficiency. The problems that motivate these protocols were revealed by timing-accurate simulation. Timing-accurate software execution exposed performance bottlenecks that I address with a new communication primitive called Conditional Immediate Transmission (CIT). I show that CIT can improve on throughput in bulk transfer scenarios, and lower latency in many-to-one convergecast networks. Timing-accurate communication exposed that the hidden terminal problem is aggravated in duty-cycled networks that experience traffic bursts. I propose the Strawman mechanism that makes a radio duty-cycled network robust against traffic bursts by efficiently coping with hidden terminals. The Cooja simulation environment is available for use by others and is the default simulator in the Contiki operating system since 2006.

  • 20944.
    Österlind, Fredrik
    et al.
    RISE, Swedish ICT, SICS.
    Dunkels, Adam
    RISE, Swedish ICT, SICS.
    Approaching the maximum 802.15.4 multi-hop throughput2008Conference paper (Refereed)
    Abstract [en]

    Recent work in sensor network energy optimization has shown that batch-and-send networks can significantly reduce network energy consumption. Batch-and-send networks rely on effective batch data transport protocols, but the throughput of state-of-the-art protocols is low. We present conditional immediate transmission, a novel packet forwarding mechanism, with which we achieve a 109 kbit/s raw data throughput over a 6-hop multi-channel 250 kbit/s 802.15.4 network; 97% of the theoretical upper bound. We show that packet copying is the bottleneck in high-throughput packet forwarding and that by moving packet copying off the critical path, we nearly double the end-to-end throughput. Our results can be seen as an upper bound on the achievable throughput over a single-route, multi-channel, multihop 802.15.4 network. While it might be possible to slightly improve our performance, we are sufficiently close to the theoretical upper bound for such work to be of limited value.

  • 20945.
    Österlind, Fredrik
    et al.
    RISE, Swedish ICT, SICS.
    Dunkels, Adam
    RISE, Swedish ICT, SICS.
    Approaching the maximum 802.15.4 multi-hop throughput2008Report (Other academic)
    Abstract [en]

    Recent work in sensor network energy optimization has shown that batch-and-send networks can significantly reduce network energy consumption. Batch-and-send networks rely on effective batch data transport protocols, but the throughput of state-of-the-art protocols is low. We present conditional immediate transmission, a novel packet forwarding mechanism, with which we achieve a 109 kbit/s raw data throughput over a 6-hop multi-channel 250 kbit/s 802.15.4 network; 97% of the theoretical upper bound. We show that packet copying is the bottleneck in high-throughput packet forwarding and that by moving packet copying off the critical path, we nearly double the end-to-end throughput. Our results can be seen as an upper bound on the achievable throughput over a single-route, multi-channel, multi-hop 802.15.4 network. While it might be possible to slightly improve our performance, we are sufficiently close to the theoretical upper bound for such work to be of limited value. Rather, our results suggests that other mechanisms, such as multi-route forwarding, may be fruitful way to further improve multi-hop throughput.

  • 20946.
    Österlind, Fredrik
    et al.
    RISE, Swedish ICT, SICS.
    Dunkels, Adam
    RISE, Swedish ICT, SICS.
    Eriksson, Joakim
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Finne, Niclas
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Voigt, Thiemo
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Cross-level sensor network simulation with COOJA2006Conference paper (Refereed)
    Abstract [en]

    Simulators for wireless sensor networks are a valuable tool for system development. However, current simulators can only simulate a single level of a system at once. This makes system development and evolution difficult since developers cannot use the same simulator for both high-level algorithm development and low-level development such as device-driver implementations. We propose cross-level simulation, a novel type of wireless sensor network simulation that enables holistic simultaneous simulation at different levels. We present an implementation of such a simulator, COOJA, a simulator for the Contiki sensor node operating system. COOJA allows for simultaneous simulation at the network level, the operating system level, and the machine code instruction set level. With COOJA, we show the feasibility of the cross-level simulation approach.

  • 20947.
    Österlind, Fredrik
    et al.
    RISE, Swedish ICT, SICS.
    Dunkels, Adam
    RISE, Swedish ICT, SICS.
    Eriksson, Joakim
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Finne, Niclas
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Voigt, Thiemo
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Cross-level sensor network simulation with Cooja2007In: Proceedings of Real-Time in Sweden 2007, 2007, 1Conference paper (Refereed)
  • 20948.
    Österlind, Fredrik
    et al.
    RISE, Swedish ICT, SICS.
    Dunkels, Adam
    RISE, Swedish ICT, SICS.
    Eriksson, Joakim
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Finne, Niclas
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Voigt, Thiemo
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Cross-level simulation in cooja.2007Conference paper (Refereed)
  • 20949.
    Österlind, Fredrik
    et al.
    RISE, Swedish ICT, SICS.
    Dunkels, Adam
    RISE, Swedish ICT, SICS.
    He, Zhitao
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Tsiftes, Nicolas
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Sensornet checkpointing between simulated and deployed networks2009In: IPSN'09, 2009, 1, , p. 2Conference paper (Refereed)
    Abstract [en]

    Sensor network development is notoriously difficult due to the low visibility of sensor platforms and systems. We propose sensornet checkpointing to increase the visibility of sensor networks. With sensornet checkpointing, we transfer network-wide application checkpoints between simulated and real networks. This approach enable advances in many research areas: visualization, repeatable experiments, fault injection, and application debugging. We demonstrate sensornet checkpointing on a network of Tmote Sky motes running Contiki.

  • 20950.
    Österlind, Fredrik
    et al.
    RISE, Swedish ICT, SICS.
    Dunkels, Adam
    RISE, Swedish ICT, SICS.
    Voigt, Thiemo
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Tsiftes, Nicolas
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Eriksson, Joakim
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Finne, Niclas
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Sensornet checkpointing: enabling repeatability in testbeds and realism in simulations2009In: 6th European Conference on Wireless Sensor Networks, 2009, 1Conference paper (Refereed)
    Abstract [en]

    When developing sensor network applications, the shift from simulation to testbed causes application failures, resulting in additional time-consuming iterations between simulation and testbed. We propose transferring sensor network checkpoints between simulation and testbed to reduce the gap between simulation and testbed. Sensornet checkpointing combines the best of both simulation and testbeds: the nonintrusiveness and repeatability of simulation, and the realism of testbeds.

416417418419420421422 20901 - 20950 of 21178
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