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  • 1.
    A. Hosseini, Vahid
    et al.
    University West, Sweden ; Innovatum AB, Sweden.
    Karlsson, Leif
    University West, Sweden.
    Örnek, Cem
    RISE - Research Institutes of Sweden, Materials and Production, KIMAB. KTH Royal Institute of Technology, Sweden.
    Reccagni, Pierfrance
    The University of Manchester, UK.
    Wessman, Sten
    University West, Sweden.
    Engelberg, Dirk
    The University of Manchester, UK.
    Microstructure and functionality of a uniquely graded super duplex stainless steel designed by a novel arc heat treatment method2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 139, p. 390-400Article in journal (Refereed)
    Abstract [en]

    A novel arc heat treatment technique was applied to design a uniquely graded super duplex stainless steel (SDSS), by subjecting a single sample to a steady state temperature gradient for 10 h. A new experimental approach was used to map precipitation in microstructure, covering aging temperatures of up to 1430 °C. The microstructure was characterized and functionality was evaluated via hardness mapping. Nitrogen depletion adjacent to the fusion boundary depressed the upper temperature limit for austenite formation and influenced the phase balance above 980 °C. Austenite/ferrite boundaries deviating from Kurdjumov–Sachs orientation relationship (OR) were preferred locations for precipitation of σ at 630–1000 °C, χ at 560–1000 °C, Cr2N at 600–900 °C and R between 550 °C and 700 °C. Precipitate morphology changed with decreasing temperature; from blocky to coral-shaped for σ, from discrete blocky to elongated particles for χ, and from polygonal to disc-shaped for R. Thermodynamic calculations of phase equilibria largely agreed with observations above 750 °C when considering nitrogen loss. Formation of intermetallic phases and 475 °C-embrittlement resulted in increased hardness. A schematic diagram, correlating information about phase contents, morphologies and hardness, as a function of exposure temperature, is introduced for evaluation of functionality of microstructures. 

  • 2.
    Aadland, Reidun C.
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Dziuba, Carter J.
    University of Calgary, Canada.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Torsæter, Ole
    NTNU Norwegian University of Science and Technology, Norway.
    Holt, Thorleif
    SINTEF, Norway.
    Gates, Ian D.
    University of Calgary, Canada.
    Bryant, Steven L.
    University of Calgary, Canada.
    Identification of nanocellulose retention characteristics in porous media2018In: Nanomaterials, ISSN 2079-4991, Vol. 8, no 7, article id 547Article in journal (Refereed)
    Abstract [en]

    The application of nanotechnology to the petroleum industry has sparked recent interest in increasing oil recovery, while reducing environmental impact. Nanocellulose is an emerging nanoparticle that is derived from trees or waste stream from wood and fiber industries. Thus, it is taken from a renewable and sustainable source, and could therefore serve as a good alternative to current Enhanced Oil Recovery (EOR) technologies. However, before nanocellulose can be applied as an EOR technique, further understanding of its transport behavior and retention in porous media is required. The research documented in this paper examines retention mechanisms that occur during nanocellulose transport. In a series of experiments, nanocellulose particles dispersed in brine were injected into sandpacks and Berea sandstone cores. The resulting retention and permeability reduction were measured. The experimental parameters that were varied include sand grain size, nanocellulose type, salinity, and flow rate. Under low salinity conditions, the dominant retention mechanism was adsorption and when salinity was increased, the dominant retention mechanism shifted towards log-jamming. Retention and permeability reduction increased as grain size decreased, which results from increased straining of nanocellulose aggregates. In addition, each type of nanocellulose was found to have significantly different transport properties. Experiments with Berea sandstone cores indicate that some pore volume was inaccessible to the nanocellulose. As a general trend, the larger the size of aggregates in bulk solution, the greater the observed retention and permeability reduction. Salinity was found to be the most important parameter affecting transport. Increased salinity caused additional aggregation, which led to increased straining and filter cake formation. Higher flow rates were found to reduce retention and permeability reduction. Increased velocity was accompanied by an increase in shear, which is believed to promote breakdown of nanocellulose aggregates. © 2018 by the authors.

  • 3.
    Aadland, Reidun
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Jakobsen, Trygve
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Long-Sanouiller, Haili
    NTNU Norwegian University of Science and Technology, Norway.
    Simon, Sebastien
    NTNU Norwegian University of Science and Technology, Norway.
    Paso, Kristofer
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Torsæter, Ole
    NTNU Norwegian University of Science and Technology, Norway.
    High-temperature core flood investigation of nanocellulose as a green additive for enhanced oil recovery2019In: Nanomaterials, ISSN 2079-4991, Vol. 9, no 5, article id 665Article in journal (Refereed)
    Abstract [en]

    Recent studies have discovered a substantial viscosity increase of aqueous cellulose nanocrystal (CNC) dispersions upon heat aging at temperatures above 90 °C. This distinct change in material properties at very low concentrations in water has been proposed as an active mechanism for enhanced oil recovery (EOR), as highly viscous fluid may improve macroscopic sweep efficiencies and mitigate viscous fingering. A high-temperature (120 °C) core flood experiment was carried out with 1 wt.% CNC in low salinity brine on a 60 cm-long sandstone core outcrop initially saturated with crude oil. A flow rate corresponding to 24 h per pore volume was applied to ensure sufficient viscosification time within the porous media. The total oil recovery was 62.2%, including 1.2% oil being produced during CNC flooding. Creation of local log-jams inside the porous media appears to be the dominant mechanism for additional oil recovery during nano flooding. The permeability was reduced by 89.5% during the core flood, and a thin layer of nanocellulose film was observed at the inlet of the core plug. CNC fluid and core flood effluent was analyzed using atomic force microscopy (AFM), particle size analysis, and shear rheology. The effluent was largely unchanged after passing through the core over a time period of 24 h. After the core outcrop was rinsed, a micro computed tomography (micro-CT) was used to examine heterogeneity of the core. The core was found to be homogeneous. © 2019 by the authors.

  • 4.
    Aaen, Ragnhild
    et al.
    Norwegian University of Science and Technology, Norway.
    Brodin, Fredrik Wernersson
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Simon, Sébastien
    Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. Norwegian University of Science and Technology, Norway.
    Oil-in-Water Emulsions Stabilized by Cellulose Nanofibrils-The Effects of Ionic Strength and pH.2019In: Nanomaterials (Basel, Switzerland), ISSN 2079-4991, Vol. 9, no 2, article id E259Article in journal (Refereed)
    Abstract [en]

    Pickering o/w emulsions prepared with 40 wt % rapeseed oil were stabilized with the use of low charged enzymatically treated cellulose nanofibrils (CNFs) and highly charged 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized CNFs. The emulsion-forming abilities and storage stability of the two qualities were tested in the presence of NaCl and acetic acid, at concentrations relevant to food applications. Food emulsions may be an important future application area for CNFs due to their availability and excellent viscosifying abilities. The emulsion characterization was carried out by visual inspection, light microscopy, viscosity measurements, dynamic light scattering and mild centrifugation, which showed that stable emulsions could be obtained for both CNF qualities in the absence of salt and acid. In addition, the enzymatically stabilized CNFs were able to stabilize emulsions in the presence of acid and NaCl, with little change in the appearance or droplet size distribution over one month of storage at room temperature. The work showed that enzymatically treated CNFs could be suitable for use in food systems where NaCl and acid are present, while the more highly charged TEMPO-CNFs might be more suited for other applications, where they can contribute to a high emulsion viscosity even at low concentrations.

  • 5.
    Aaen, Ragnhild
    et al.
    Norwegian University of Science and Technology, Norway.
    Simon, Sebastien
    Norwegian University of Science and Technology, Norway.
    Wernersson Brodin, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. Norwegian University of Science and Technology, Norway.
    The potential of TEMPO-oxidized cellulose nanofibrils as rheology modifiers in food systems2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 9, p. 5483-5496Article in journal (Refereed)
    Abstract [en]

    Abstract: Cellulose nanofibrils (CNFs) have been proposed for use in low-fat food products due to their availability and excellent viscosifying and gel forming abilities. As the CNFs are negatively charged, the presence of other components in foods, such as electrolytes and food additives such as xanthan gum is likely to affect their rheological properties. Hence, the study of these interactions can contribute valuable information of the suitability of CNFs as rheology modifiers and fat replacers. Rheological measurements on aqueous dispersions of TEMPO-oxidized CNFs were performed with variations in concentration of CNFs, concentration of electrolytes and with varying CNF/xanthan ratios. UV–Vis Spectroscopy was used to evaluate the onset of CNF flocculation/aggregation in the presence of electrolytes. The CNF dispersions followed a power-law dependency for viscosity and moduli on CNF concentration. Low electrolyte additions strengthened the CNF network by allowing for stronger interactions, while higher additions led to fibril aggregation, and loss of viscosity, especially under shear. The CNF/xanthan ratio, as well as the presence of electrolytes were shown to be key factors in determining whether the viscosity and storage modulus of CNF dispersions increased or decreased when xanthan was added. Graphical abstract: [Figure not available: see fulltext.].

  • 6.
    Aarstad, Olav
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Pedersen, Ina Sander
    NTNU Norwegian University of Science and Technology, Norway.
    Björnöy, Sindre H.
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Strand, Berit L.
    NTNU Norwegian University of Science and Technology, Norway.
    Mechanical properties of composite hydrogels of alginate and cellulose nanofibrils2017In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 9, no 8, article id 378Article in journal (Refereed)
    Abstract [en]

    Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering.

  • 7.
    Abbas, Mohammad
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Inayat, Irum
    National University of Computer & Emerging Sciences, Pakistan.
    Saadatmand, Mehrdad
    RISE - Research Institutes of Sweden, ICT, SICS.
    Jan, Naila
    National University of Computer & Emerging Sciences, Pakistan.
    Requirements dependencies-based test case prioritization for extra-functional properties2019In: Proceedings - 2019 IEEE 12th International Conference on Software Testing, Verification and Validation Workshops, ICSTW 2019, Institute of Electrical and Electronics Engineers Inc. , 2019, p. 159-163Conference paper (Refereed)
    Abstract [en]

    The use of requirements' information in testing is a well-recognized practice in the software development life cycle. Literature reveals that existing tests prioritization and selection approaches neglected vital factors affecting tests priorities, like interdependencies between requirement specifications. We believe that models may play a positive role in specifying these inter-dependencies and prioritizing tests based on these inter-dependencies. However, till date, few studies can be found that make use of requirements inter-dependencies for test case prioritization. This paper uses a meta-model to aid modeling requirements, their related tests, and inter-dependencies between them. The instance of this meta-model is then processed by our modified PageRank algorithm to prioritize the requirements. The requirement priorities are then propagated to related test cases in the test model and test cases are selected based on coverage of extra-functional properties. We have demonstrated the applicability of our proposed approach on a small example case.

  • 8.
    Abbas, Nadeem
    et al.
    Linnaeus University, Sweden.
    Andersson, Jesper
    Linnaeus University, Sweden.
    Architectural Reasoning Support for Product-Lines of Self-adaptive Software Systems - A Case Study2015In: Software Architecture: 9th European Conference, ECSA 2015, Dubrovnik/Cavtat, Croatia, September 7-11, 2015. Proceedings, Springer International Publishing , 2015, 17, p. 20-36Chapter in book (Refereed)
    Abstract [en]

    Software architecture serves as a foundation for the design and development of software systems. Designing an architecture requires extensive analysis and reasoning. The study presented herein focuses on the architectural analysis and reasoning in support of engineering self-adaptive software systems with systematic reuse. Designing self-adaptive software systems with systematic reuse introduces variability along three dimensions; adding more complexity to the architectural analysis and reasoning process. To this end, the study presents an extended Architectural Reasoning Framework with dedicated reasoning support for self-adaptive systems and reuse. To evaluate the proposed framework, we conducted an initial feasibility case study, which concludes that the proposed framework assists the domain architects to increase reusability, reduce fault density, and eliminate differences in skills and experiences among architects, which were our research goals and are decisive factors for a system’s overall quality.

  • 9.
    Abbas, Nadeem
    et al.
    Linnaeus University, Sweden.
    Andersson, Jesper
    Linnaeus University, Sweden.
    Harnessing Variability in Product-lines of Self-adaptive Software Systems2015In: Proceedings of the 19th International Conference on Software Product Line (SPLC '15), New York, NY, USA: Association for Computing Machinery (ACM), 2015, 12, p. 191-200Conference paper (Refereed)
    Abstract [en]

    This work studies systematic reuse in the context of self-adaptive software systems. In our work, we realized that managing variability for such platforms is different compared to traditional platforms, primarily due to the run-time variability and system uncertainties. Motivated by the fact that recent trends show that self-adaptation will be used more often in future system generation and that software reuse state-of-practice or research do not provide sufficient support, we have investigated the problems and possibly resolutions in this context. We have analyzed variability for these systems, using a systematic reuse prism, and identified a research gap in variability management. The analysis divides variability handling into four activities: (1) identify variability, (2) constrain variability, (3) implement variability, and (4) manage variability. Based on the findings we envision a reuse framework for the specific domain and present an example framework that addresses some of the identified challenges. We argue that it provides basic support for engineering self-adaptive software systems with systematic reuse. We discuss some important avenues of research for achieving the vision.

  • 10.
    Abbas, Zainab
    et al.
    KTH Royal Institute of Technology, Sweden.
    Al-Shishtawy, Ahmad
    RISE - Research Institutes of Sweden, ICT, SICS.
    Girdzijauskas, Sarunas
    RISE - Research Institutes of Sweden, ICT, SICS. KTH Royal Institute of Technology, Sweden.
    Vlassov, Vladimir
    KTH Royal Institute of Technology, Sweden.
    Short-Term Traffic Prediction Using Long Short-Term Memory Neural Networks2018In: Proceedings - 2018 IEEE International Congress on Big Data, BigData Congress 2018 - Part of the 2018 IEEE World Congress on Services, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 57-65Conference paper (Refereed)
    Abstract [en]

    Short-term traffic prediction allows Intelligent Transport Systems to proactively respond to events before they happen. With the rapid increase in the amount, quality, and detail of traffic data, new techniques are required that can exploit the information in the data in order to provide better results while being able to scale and cope with increasing amounts of data and growing cities. We propose and compare three models for short-term road traffic density prediction based on Long Short-Term Memory (LSTM) neural networks. We have trained the models using real traffic data collected by Motorway Control System in Stockholm that monitors highways and collects flow and speed data per lane every minute from radar sensors. In order to deal with the challenge of scale and to improve prediction accuracy, we propose to partition the road network into road stretches and junctions, and to model each of the partitions with one or more LSTM neural networks. Our evaluation results show that partitioning of roads improves the prediction accuracy by reducing the root mean square error by the factor of 5. We show that we can reduce the complexity of LSTM network by limiting the number of input sensors, on average to 35% of the original number, without compromising the prediction accuracy. .

  • 11.
    Abbas, Zainab
    et al.
    KTH Royal Institute of Technology, Sweden.
    Sigurdsson, Thorsteinn
    KTH Royal Institute of Technology, Sweden.
    Al-Shishtawy, Ahmad
    RISE - Research Institutes of Sweden, ICT, SICS.
    Vlassov, Vladimir
    KTH Royal Institute of Technology, Sweden.
    Evaluation of the use of streaming graph processing algorithms for road congestion detection2018In: Proceedings - 16th IEEE International Symposium on Parallel and Distributed Processing with Applications, 17th IEEE International Conference on Ubiquitous Computing and Communications, 8th IEEE International Conference on Big Data and Cloud Computing, 11th IEEE International Conference on Social Computing and Networking and 8th IEEE International Conference on Sustainable Computing and Communications, ISPA/IUCC/BDCloud/SocialCom/SustainCom 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 1017-1025Conference paper (Refereed)
    Abstract [en]

    Real-time road congestion detection allows improving traffic safety and route planning. In this work, we propose to use streaming graph processing algorithms for road congestion detection and evaluate their accuracy and performance. We represent road infrastructure sensors in the form of a directed weighted graph and adapt the Connected Components algorithm and some existing graph processing algorithms, originally used for community detection in social network graphs, for the task of road congestion detection. In our approach, we detect Connected Components or communities of sensors with similarly weighted edges that reflect different states in the traffic, e.g., free flow or congested state, in regions covered by detected sensor groups. We have adapted and implemented the Connected Components and community detection algorithms for detecting groups in the weighted sensor graphs in batch and streaming manner. We evaluate our approach by building and processing the road infrastructure sensor graph for Stockholm's highways using real-world data from the Motorway Control System operated by the Swedish traffic authority. Our results indicate that the Connected Components and DenGraph community detection algorithms can detect congestion with accuracy up to ? 94% for Connected Components and up to ? 88% for DenGraph. The Louvain Modularity algorithm for community detection fails to detect congestion regions for sparsely connected graphs, representing roads that we have considered in this study. The Hierarchical Clustering algorithm using speed and density readings is able to detect congestion without details, such as shockwaves.

  • 12.
    Abbasi, Abdul Gahafoor
    et al.
    RISE - Research Institutes of Sweden, ICT, Acreo.
    Khan, Zaheer
    University of the West of England, UK.
    Veidblock: Verifiable identity using blockchain and ledger in a software defined network2017In: UCC 2017 Companion - Companion Proceedings of the 10th International Conference on Utility and Cloud Computing, Association for Computing Machinery, Inc , 2017, p. 173-179Conference paper (Refereed)
    Abstract [en]

    Blockchain and verifiable identities have a lot of potential in future distributed software applications e.g. smart cities, eHealth, autonomous vehicles, networks, etc. In this paper, we proposed a novel technique, namely VeidBlock 1 , to generate verifiable identities by following a reliable authentication process. These entities are managed by using the concepts of blockchain ledger and distributed through an advance mechanism to protect them against tampering. All identities created using VeidBlock approach are verifiable and anonymous therefore it preserves user’s privacy in verification and authentication phase. As a proof of concept, we implemented and tested the VeidBlock protocols by integrating it in a SDN based infrastructure. Analysis of the test results yield that all components successfully and autonomously performed initial authentication and locally verified all the identities of connected components.

  • 13.
    Abbaspour Assadollah, Sara
    et al.
    Mälardalen University, Sweden.
    Saadatmand, Mehrdad
    RISE, Swedish ICT, SICS.
    Eldh, Sigrid
    Ericsson AB, Sweden.
    Sundmark, Daniel
    Mälardalen University, Sweden.
    Hansson, Hans
    Mälardalen University, Sweden.
    A Model for Systematic Monitoring and Debugging of Starvation Bugs in Multicore Software2016In: Proceedings of the 1st International Workshop on Specification, Comprehension, Testing, and Debugging of Concurrent Programs (SCTDCP 2016), 2016, p. 7-11Conference paper (Refereed)
    Abstract [en]

    With the development of multicore hardware, concurrent, parallel and multicore software are becoming increasingly popular. Software companies are spending a huge amount of time and resources to nd and debug the bugs. Among all types of software bugs, concurrency bugs are also important and troublesome. This type of bugs is increasingly becoming an issue particularly due to the growing prevalence of multicore hardware. In this position paper, we propose a model for monitoring and debugging Starvation bugs as a type of concurrency bugs in multicore software. The model is composed into three phases: monitoring, detecting and debugging. The monitoring phase can support detecting phase by storing collected data from the system execution. The detecting phase can support debugging phase by comparing the stored data with starvation bug's properties, and the debugging phase can help in reproducing and removing the Starvation bug from multicore software. Our intention is that our model is the basis for developing tool(s) to enable solving Starvation bugs in software for multicore platforms.

  • 14.
    Abdelraheem, Mohamed Ahmed
    et al.
    RISE, Swedish ICT, SICS.
    Alizadeh, Javad
    Sharif University of Technology, Iran.
    Alkhzaimi, Hoda A.
    DTU Technical University of Denmark, Denmark.
    Aref, Mohammad Reza
    Sharif University of Technology, Iran.
    Bagheri, Nasour
    Shahid Rajaee Teachers Training University, Iran; IPM Institute for Research in Fundamental Sciences, Iran.
    Gauravaram, Praveen
    Queensland University of Technology, Australia.
    Improved Linear Cryptanalysis of reduced-round SIMON-32 and SIMON-482015In: Progress in Cryptology -- INDOCRYPT 2015, 2015, Vol. 9462, p. 153-179Conference paper (Refereed)
    Abstract [en]

    In this paper we analyse two variants of SIMON family of light-weight block ciphers against linear cryptanalysis and present the best linear cryptanalytic results on these variants of reduced-round SIMON to date. We propose a time-memory trade-off method that finds differential/linear trails for any permutation allowing low Hamming weight differential/linear trails. Our method combines low Hamming weight trails found by the correlation matrix representing the target permutation with heavy Hamming weight trails found using a Mixed Integer Programming model representing the target differential/linear trail. Our method enables us to find a 17-round linear approximation for SIMON-48 which is the best current linear approximation for SIMON-48. Using only the correlation matrix method, we are able to find a 14-round linear approximation for SIMON-32 which is also the current best linear approximation for SIMON-32. The presented linear approximations allow us to mount a 23-round key recovery attack on SIMON-32 and a 24-round Key recovery attack on SIMON-48/96 which are the current best results on SIMON-32 and SIMON-48. In addition we have an attack on 24 rounds of SIMON-32 with marginal complexity.

  • 15.
    Abdelraheem, Mohamed Ahmed
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Andersson, Tobias
    RISE - Research Institutes of Sweden, ICT, SICS.
    Gehrmann, Christian
    Lund university, Sweden.
    Searchable Encrypted Relational Databases:Risks and Countermeasures2017In: Data Privacy Management, Cryptocurrencies and Blockchain Technology: ESORICS 2017 International Workshops, DPM 2017 and CBT 2017, Oslo, Norway, September 14-15, 2017, Proceedings / [ed] Joaquin Garcia-Alfaro et al., Gewerbestrasse 11, 6330 Cham, Switzerland: Springer Nature , 2017, Vol. 10436, p. 70-85Conference paper (Refereed)
    Abstract [en]

    We point out the risks of protecting relational databases viaSearchable Symmetric Encryption (SSE) schemes by proposing an infer-ence attack exploiting the structural properties of relational databases.We show that record-injection attacks mounted on relational databaseshave worse consequences than their file-injection counterparts on un-structured databases. Moreover, we discuss some techniques to reducethe effectiveness of inference attacks exploiting the access pattern leak-age existing in SSE schemes. To the best of our knowledge, this is thefirst work that investigates the security of relational databases protectedby SSE schemes.

  • 16.
    Abdelraheem, Mohamed
    et al.
    Intelligent Voice Ltd, UK.
    Andersson, Tobias
    RISE - Research Institutes of Sweden, ICT, SICS.
    Gehrmann, Christian
    Lund University, Sweden.
    Glackin, Cornelius
    Intelligent Voice Ltd, UK.
    Practical Attacks on Relational Databases Protected via Searchable Encryption2018In: Lecture Notes in Computer Science, 2018, p. 171-191Conference paper (Refereed)
    Abstract [en]

    Searchable symmetric encryption (SSE) schemes are commonly proposed to enable search in a protected unstructured documents such as email archives or any set of sensitive text files. However, some SSE schemes have been recently proposed in order to protect relational databases. Most of the previous attacks on SSE schemes have only targeted its common use case, protecting unstructured data. In this work, we propose a new inference attack on relational databases protected via SSE schemes. Our inference attack enables a passive adversary with only basic knowledge about the meta-data information of the target relational database to recover the attribute names of some observed queries. This violates query privacy since the attribute name of a query is secret.

  • 17.
    Abdelraheem, Mohammed Ahmed
    et al.
    RISE, Swedish ICT, SICS, Security Lab.
    Gehrmann, Christian
    RISE, Swedish ICT, SICS, Security Lab.
    Lindström, Malin
    Blekinge Institute of Technology, Sweden.
    Nordahl, Christian
    Blekinge Institute of Technology, Sweden.
    Executing Boolean Queries on an Encrypted Bitmap Index2016In: CCSW 2016: Proceedings of the 2016 ACM on Cloud Computing Security Workshop, 2016, p. 11-22Conference paper (Refereed)
    Abstract [en]

    We propose a simple and efficient searchable symmetric encryption scheme based on a Bitmap index that evaluates Boolean queries. Our scheme provides a practical solution in settings where communications and computations are very constrained as it offers a suitable trade-off between privacy and performance.

  • 18. Abele, S
    et al.
    Sjöberg, M
    YKI – Ytkemiska institutet.
    Hamaide, T
    Zicmanis, A
    Guyot, A
    Reactive surfactants in heterophase polymerization. 10. Characterization of the surface activity of new polymerizable surfactants derived from maleic anhydride1997In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 13, p. 176-181Article in journal (Refereed)
    Abstract [en]

    Characterization of the surface activity of previously obtained polymerizable dialkyl maleates is performed to find out the relation between the structure of surfactants and their performances. The given polymerizable surfactants were synthesized for using in the emulsion polymerization. Three groups of dialkyl maleates-nonionic, cationic and zwitterionic-with different chain lengths of hydrophobic alkyl groups are investigated. Critical micelle concentration (cmc) values are determined for water soluble surfactants. It is found that cmc decreases with increasing chain length of the hydrophobic alkyl group. For nonionic and cationic surfactants interfacial tension at the interface between water and dodecane is measured. Droplet size in oil-in-water (O/W) emulsions is determined for all given surfactants. Cationic and zwitterionic dialkyl maleates with the longest investigated alkyl chain (R=C16H33, C17H35) provide good stability of O/W emulsions. In order to compare the obtained results, measurements with well-known surfactants-nonionic nonylphenol-poly(ethylene oxide) (NPEO10) and cationic hexadecyltrimethyl ammonium bromide (CTAB)-are performed.

  • 19. Aberer, Karl
    et al.
    Onana Alima, Luc
    RISE, Swedish ICT, SICS.
    Ghodsi, Ali
    RISE, Swedish ICT, SICS.
    Girdzijauskas, Sarunas
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    Hauswirth, Manfred
    Haridi, Seif
    RISE, Swedish ICT, SICS, Computer Systems Laboratory.
    The essence of P2P: A reference architecture for overlay networks2005Conference paper (Refereed)
    Abstract [en]

    The success of the P2P idea has created a huge diversity of approaches, among which overlay networks, for example, Gnutella, Kazaa, Chord, Pastry, Tapestry, P-Grid, or DKS, have received specific attention from both developers and researchers. A wide variety of algorithms, data structures, and architectures have been proposed. The terminologies and abstractions used, however, have become quite inconsistent since the P2P paradigm has attracted people from many different communities, e.g., networking, databases, distributed systems, graph theory, complexity theory, biology, etc. In this paper we propose a reference model for overlay networks which is capable of modeling different approaches in this domain in a generic manner. It is intended to allow researchers and users to assess the properties of concrete systems, to establish a common vocabulary for scientific discussion, to facilitate the qualitative comparison of the systems, and to serve as the basis for defining a standardized API to make overlay networks interoperable.

  • 20.
    Abitbol, Tiffany
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
    Impact of surface charge on CNC phase separation and rheology2017In: International Conference on Nanotechnology for Renewable Materials 2017, TAPPI Press , 2017, p. 64-71Conference paper (Refereed)
  • 21.
    Abitbol, Tiffany
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, Biorefinery and Energy.
    Ahniyaz, Anwar
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    Swerin, Agne
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    UV-blocking hybrid nanocellulose films containing ceria and silica nanoparticles2018In: International Conference on Nanotechnology for Renewable Materials 2018, 2018, p. 503-515Conference paper (Refereed)
  • 22.
    Abitbol, Tiffany
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation. The Hebrew University of Jerusalem, Israel.
    Kam, Doron
    The Hebrew University of Jerusalem, Israel.
    Levi-Kalisman, Yael
    The Hebrew University of Jerusalem, Israel.
    Gray, Derek G
    McGill University, Canada.
    Shoseyov, Oded
    The Hebrew University of Jerusalem, Israel.
    Surface Charge Influence on the Phase Separation and Viscosity of Cellulose Nanocrystals2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 13, p. 3925-3933Article in journal (Refereed)
    Abstract [en]

    counterions in the suspensions. The results suggest that there is a threshold surface charge density (∼0.3%S) above which effective volume considerations are dominant across the concentration range relevant to liquid crystalline phase formation. Above this threshold value, phase separation occurs at the same effective volume fraction of CNCs (∼10 vol %), with a corresponding increase in critical concentration due to the decrease in effective diameter that occurs with increasing surface charge. Below or near this threshold value, the formation of end-to-end aggregates may favor gelation and interfere with ordered phase formation.

  • 23.
    Abitbol, Tobias
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    Ahniyaz, Anwar
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    Swerin, Agne
    RISE - Research Institutes of Sweden, Bioscience and Materials, Surface, Process and Formulation.
    UV-blocking hybrid nanocellulose films containing ceria and silica nanoparticles2018In: International Conference on Nanotechnology for Renewable Materials 2018, 2018, p. 503-515Conference paper (Refereed)
  • 24. Abletshauser, C
    et al.
    Klüssendorf, D
    Schmidt, A
    Winkler, K
    März, W
    Buddecke, E
    Malmsten, M
    YKI – Ytkemiska institutet.
    Biosensing of arteriosclerotic nanoplaque formation and interaction with an HMG-CoA reductase inhibitor2002In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 176, p. 131-146Article in journal (Refereed)
    Abstract [en]

    Proteoheparan sulphate can be adsorbed to a methylated silica surface in a monomolecular layer via its transmembrane hydrophobic protein core domain. As a result of electrostatic repulsion, its anionic glycosaminoglycan side chains are stretched out into the blood substitute solution, thereby representing one receptor site for specific lipoprotein binding through basic amino acid-rich residues within their apolipoproteins. The binding process was studied by ellipsometric techniques suggesting that high-density lipoprotein (HDL) has a high binding affinity and a protective effect on interfacial heparan sulphate proteoglycan layers with respect to low-density lipoprotein (LDL) and Ca2+ complexation. Low-density lipoprotein was found to deposit strongly at the proteoheparan sulphate-coated surface, particularly in the presence of Ca2+, apparently through complex formation 'proteoglycan-LDL-calcium'. This ternary complex build-up may be interpreted as arteriosclerotic nanoplaque formation on the molecular level responsible for the arteriosclerotic primary lesion. On the other hand, HDL bound to heparan sulphate proteoglycan protected against LDL deposition and completely suppressed calcification of the proteoglycan-lipoprotein complex. In addition, HDL was able to decelerate the ternary complex deposition. Therefore, HDL attached to its proteoglycan receptor sites is thought to raise a multidomain barrier, selection and control motif for transmembrane and paracellular lipoprotein uptake into the arterial wall. Although much remains unclear regarding the mechanism of lipoprotein depositions at proteoglycan-coated surfaces, it seems clear that the use of such systems offers possibilities for investigating lipoprotein deposition at a 'nanoscopic' level under close to physiological conditions. In particular, Ca2+-promoted LDL deposition and the protective effect of HDL even at high Ca2+ and LDL concentrations agree well with previous clinical observations regarding risk and beneficial factors for early stages of atherosclerosis. Considering this, the system was tested on its reliability in a biosensor application in order to unveil possible acute pleiotropic effects of the lipid lowering drug fluvastatin. The very low-density lipoprotein (VLDL)/intermediate-density lipoprotein (IDL)/LDL plasma fraction from a high risk patient with dyslipoproteinaemia and type 2 diabetes mellitus showed beginning arteriosclerotic nanoplaque formation already at a normal blood Ca2+ concentration, with a strong increase at higher Ca2+ concentrations. Fluvastatin, whether applied to the patient (one single 80 mg slow release matrix tablet) or acutely in the experiment (2.2 μmol L-1), markedly slowed down this process of ternary aggregational nanoplaque complexation at all Ca2+ concentrations used. This action resulted without any significant change in lipid concentrations of the patient. Furthermore, after ternary complex build-up, fluvastatin, similar to HDL, was able to reduce nanoplaque adsorption and size. These immediate effects of fluvastatin have to be taken into consideration while interpreting the clinical outcome of long-term studies.

  • 25. Abraham, T
    et al.
    Kumpulainen, A
    Xu, Z
    Rutland, M
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Masliyah, J
    Polyelectrolyte-mediated interaction between similarly charged surfaces: Role of divalent counter ions in tuning surface forces2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, p. 8321-8327Article in journal (Refereed)
    Abstract [en]

    The effects of divalent salts (CaCl2, MgCl2 and BaCl2) in promoting the adsorption of weakly charged polyelectrolyte (polyacrylic acid), PAA, Mw ~ 250000 g/mol) on mica surfaces and their role in tuning the nature of interactions between such adsorbed polyelectrolyte layers were studied using the interferometric surface forces apparatus. With mica surfaces in 3 mM MgCl2 solutions at pH ~8.0-9.0, the addition of 10 ppm PAA resulted in a long-range attractive bridging force and a short-range repulsive steric force. This force profile indicates a low surface coverage and weak adsorption. The range of the force can be related to the characteristic length scale RG of polyelectrolyte chains using a scaling description. An increase of the PAA concentration to 50 ppm changed the attractive force profile to a monotonic, long-range repulsive interaction extending up to 600 Å due to the increased surface coverage of polyelectrolyte chains on the mica surfaces. Comparison of the measured forces with a scaling mean field model suggests that the adsorbed polyelectrolyte chains are stretched, which eventually give rise to the polyelectrolyte brush like structure. When the mica surfaces were preincubated in 3 mM CaCl2 at pH ~8.0-9.0, in contrast to the case of 3 mM MgCl2, the addition of 10 ppm PAA resulted in a more complex force profile: long-range repulsive forces extending up to 800 Å followed by an attractive force regime and a second repulsive force regime at shorter separations. The long-range electrosteric forces can be attributed to strong adsorption of polyelectrolyte chains on mica surfaces (high surface coverage) which is facilitated by the presence of Ca2+ ions, while the intermediate range attractive forces can be ascribed to Ca2+ assisted bridging between adsorbed polyelectrolyte chains. Also interesting is to note various relaxation processes present in this system. In contrast to both MgCl2 and CaCl2 systems, with mica surfaces in 3 mM BaCl2 solution at pH ~8.0-9.0, the addition of 10 ppm PAA resulted in precipitation of polyelectrolyte chains on mica surfaces, resulting in an extremely long-range monotonic repulsive force profile. In summary, our study showed that divalent counterions (Mg2+, Ca2+, and Ba2+) exhibit significantly different behavior in promoting PAA adsorption on mica surfaces, modifying and controlling various surface interactions.

  • 26. Abrahamsson, C.
    et al.
    Nordstierna, L.
    Bergenholtz, J.
    Altskär, Annika
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Magnetically induced structural anisotropy in binary colloidal gels and its effect on diffusion and pressure driven permeability2014In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, no 24, p. 4403-4412Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis, microstructure and mass transport properties of a colloidal hydrogel self-assembled from a mixture of colloidal silica and nontronite clay plates at different particle concentrations. The gel-structure had uniaxial long-range anisotropy caused by alignment of the clay particles in a strong external magnetic field. After gelation the colloidal silica covered the clay particle network, fixing the orientation of the clay plates. Comparing gels with a clay concentration between 0 and 0.7 vol%, the magnetically oriented gels had a maximum water permeability and self-diffusion coefficient at 0.3 and 0.7 vol% clay, respectively. Hence the specific clay concentration resulting in the highest liquid flux was pressure dependent. This study gives new insight into the effect of anisotropy, particle concentration and bound water on mass transport properties in nano/microporous materials. Such findings merit consideration when designing porous composite materials for use in for example fuel cell, chromatography and membrane technology. © 2014 the Partner Organisations.

  • 27. Abrahamsson, C.
    et al.
    Siahpoosh, M.
    Altskär, Annika
    SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Composite silica gel as test bed for flow in nano porous materials2011In: European Cells and Materials, ISSN 1473-2262, E-ISSN 1473-2262, Vol. 21, no SUPPL.1, p. 27-Article in journal (Refereed)
  • 28.
    Abrahamsson, Henrik
    RISE, Swedish ICT, SICS. School of Innovation, Design and Engineering.
    Network overload avoidance by traffic engineering and content caching2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The Internet traffic volume continues to grow at a great rate, now driven by video and TV distribution. For network operators it is important to avoid congestion in the network, and to meet service level agreements with their customers. This thesis presents work on two methods operators can use to reduce links loads in their networks: traffic engineering and content caching. This thesis studies access patterns for TV and video and the potential for caching. The investigation is done both using simulation and by analysis of logs from a large TV-on-Demand system over four months. The results show that there is a small set of programs that account for a large fraction of the requests and that a comparatively small local cache can be used to significantly reduce the peak link loads during prime time. The investigation also demonstrates how the popularity of programs changes over time and shows that the access pattern in a TV-on-Demand system very much depends on the content type. For traffic engineering the objective is to avoid congestion in the network and to make better use of available resources by adapting the routing to the current traffic situation. The main challenge for traffic engineering in IP networks is to cope with the dynamics of Internet traffic demands. This thesis proposes L-balanced routings that route the traffic on the shortest paths possible but make sure that no link is utilised to more than a given level L. L-balanced routing gives efficient routing of traffic and controlled spare capacity to handle unpredictable changes in traffic. We present an L-balanced routing algorithm and a heuristic search method for finding L-balanced weight settings for the legacy routing protocols OSPF and IS-IS. We show that the search and the resulting weight settings work well in real network scenarios.

  • 29.
    Abrahamsson, Henrik
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Traffic measurement and analysis1999Report (Other academic)
    Abstract [en]

    Measurement and analysis of real traffic is important to gain knowledge about the characteristics of the traffic. Without measurement, it is impossible to build realistic traffic models. It is recent that data traffic was found to have self-similar properties. In this thesis work traffic captured on the network at SICS and on the Supernet, is shown to have this fractal-like behaviour. The traffic is also examined with respect to which protocols and packet sizes are present and in what proportions. In the SICS trace most packets are small, TCP is shown to be the predominant transport protocol and NNTP the most common application. In contrast to this, large UDP packets sent between not well-known ports dominates the Supernet traffic. Finally, characteristics of the client side of the WWW traffic are examined more closely. In order to extract useful information from the packet trace, web browsers use of TCP and HTTP is investigated including new features in HTTP/1.1 such as persistent connections and pipelining. Empirical probability distributions are derived describing session lengths, time between user clicks and the amount of data transferred due to a single user click. These probability distributions make up a simple model of WWW-sessions.

  • 30.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Ahlgren, Bengt
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Temporal Characteristics of Large IP Traffic Flows2003Report (Other academic)
    Abstract [en]

    Several studies of Internet traffic have shown that it is a small percentage of the flows that dominate the traffic. This is often referred to as the mice and elephants phenomenon. It has been proposed that this might be one of very few invariants of Internet traffic and that this property could somehow be used for traffic engineering purposes. The idea being that one in a scalable way could control a major part of the traffic by only keeping track of a small number of flows. But for this the large flows must also be stable in the meaning that they should be among the largest flows during long periods of time. In this work we analyse packet traces of Internet traffic and study the temporal characteristics of large aggregated traffic flows defined by destination address prefixes.

  • 31.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Ahlgren, Bengt
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Using empirical distributions to characterize web client traffic and to generate synthetic traffic2000Conference paper (Refereed)
  • 32.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Ahlgren, Bengt
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Alonso, Juan
    RISE - Research Institutes of Sweden, ICT, SICS.
    Andersson, Anders
    RISE - Research Institutes of Sweden, ICT, SICS.
    Kreuger, Per
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    A Multi Path Routing Algorithm for IP Networks Based on Flow Optimisation.2002Conference paper (Refereed)
  • 33.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Ahlgren, Bengt
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Alonso, Juan
    RISE - Research Institutes of Sweden, ICT, SICS.
    Andersson, Anders
    RISE - Research Institutes of Sweden, ICT, SICS.
    Kreuger, Per
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    From QoS provisioning to QoS charging2002In: Proceedings of the Second International Workshop on Internet Charging and QoS Technologies, ICQT 2002, 2002, 1, Vol. Lectures Notes in Computer Science (LNCS) no. 2511, p. 135-144Conference paper (Refereed)
  • 34.
    Abrahamsson, Henrik
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ahlgren, Bengt
    RISE - Research Institutes of Sweden, ICT, SICS.
    Lindvall, Patrik
    TeliaSonera, Sweden.
    Nieminen, Johanna
    TeliaSonera, Sweden.
    Tholin, Per
    TeliaSonera, Sweden.
    Traffic Characteristics on 1Gbit/s Access Aggregation Links2017Conference paper (Refereed)
    Abstract [en]

    Large network operators have thousands or tens of thousands of access aggregation links that they need to manage and dimension properly. Measuring and understanding the traffic characteristics on these type of links are therefore essential. What do the traffic intensity characteristics look like on different timescales from days down to milliseconds? How do the characteristics differ if we compare links with the same capacity but with different type of clients and access technologies? How do the traffic characteristics differ from that on core network links? These are the type of questions we set out to investigate in this paper. We present the results of packet level measurements on three different 1Gbit/s aggregation links in an operational IP network. We see large differences in traffic characteristics between the three links. We observe highly skewed link load probability densities on timescales relevant for buffering (i.e. 10-milliseconds). We demonstrate the existence of large traffic spikes on short timescales (10-100ms) and show their impact on link delay. We also found that these traffic bursts often are caused by only one or a few IP flows.

  • 35.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Ahlgren, Bengt
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Tholin, Per
    TeliaSonera, Sweden.
    Delay and Traffic Intensity Monitoring in an Operational IP Network2015In: 11th Swedish National Computer Networking Workshop (SNCNW 2015), Karlstad, Sweden, 2015, 6Conference paper (Refereed)
  • 36.
    Abrahamsson, Henrik
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ben Abdesslem, Fehmi
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ahlgren, Bengt
    RISE - Research Institutes of Sweden, ICT, SICS.
    Björkman, Mats
    Mälardalen University, Sweden.
    Brunstrom, Anna
    Karlstad University, Sweden.
    Marsh, Ian
    RISE - Research Institutes of Sweden, ICT, SICS.
    Selecting Operator in 3G/4G Networks for Time-Critical C-ITS Applications2018Conference paper (Refereed)
  • 37.
    Abrahamsson, Henrik
    et al.
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ben Abdesslem, Fehmi
    RISE - Research Institutes of Sweden, ICT, SICS.
    Ahlgren, Bengt
    RISE - Research Institutes of Sweden, ICT, SICS.
    Brunstrom, Anna
    Karlstad University, Sweden.
    Marsh, Ian
    RISE - Research Institutes of Sweden, ICT, SICS.
    Björkman, Mats
    Mälardalen University, Sweden.
    Connected Vehicles in Cellular Networks: Multi-access versus Single-access Performance2018Conference paper (Refereed)
    Abstract [en]

    Connected vehicles can make roads traffic safer andmore efficient, but require the mobile networks to handle timecriticalapplications. Using the MONROE mobile broadbandmeasurement testbed we conduct a multi-access measurementstudy on buses. The objective is to understand what networkperformance connected vehicles can expect in today’s mobilenetworks, in terms of transaction times and availability. The goalis also to understand to what extent access to several operatorsin parallel can improve communication performance.In our measurement experiments we repeatedly transfer warningmessages from moving buses to a stationary server. Wetriplicate the messages and always perform three transactionsin parallel over three different cellular operators. This creates adataset with which we can compare the operators in an objectiveway and with which we can study the potential for multi-access.In this paper we use the triple-access dataset to evaluate singleaccessselection strategies, where one operator is chosen for eachtransaction. We show that if we have access to three operatorsand for each transaction choose the operator with best accesstechnology and best signal quality then we can significantlyimprove availability and transaction times compared to theindividual operators. The median transaction time improves with6% compared to the best single operator and with 61% comparedto the worst single operator. The 90-percentile transaction timeimproves with 23% compared to the best single operator andwith 65% compared to the worst single operator.

  • 38.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Björkman, Mats
    Caching for IPTV distribution with time-shift2013Conference paper (Refereed)
  • 39.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Björkman, Mats
    Robust Traffic Engineering using L-balanced Weight-Settings in OSPF/IS-IS2009Conference paper (Refereed)
  • 40.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Björkman, Mats
    Simulation of IPTV caching strategies2010Conference paper (Refereed)
    Abstract [en]

    IPTV, where television is distributed over the Internet Protocol in a single operator network, has become popular and widespread. Many telecom and broadband companies have become TV providers and distribute TV channels using multicast over their backbone networks. IPTV also means an evolution to time-shifted television where viewers now often can choose to watch the programs at any time. However, distributing individual TV streams to each viewer requires a lot of bandwidth and is a big challenge for TV operators. In this paper we present an empirical IPTV workload model, simulate IPTV distribution with time-shift, and show that local caching can limit the bandwidth requirements significantly.

  • 41.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Gunnar, Anders
    RISE, Swedish ICT, SICS.
    Traffic engineering in ambient networks: challenges and approaches2004In: Swedish National Computer Networking Workshop, 2004, 1Conference paper (Refereed)
    Abstract [en]

    The focus of this paper is on traffic engineering in ambient networks. We describe and categorize different alternatives for making the routing more adaptive to the current traffic situation and discuss the challenges that ambient networks pose on traffic engineering methods. One of the main objectives of traffic engineering is to avoid congestion by controlling and optimising the routing function, or in short, to put the traffic where the capacity is. The main challenge for traffic engineering in ambient networks is to cope with the dynamics of both topology and traffic demands. Mechanisms are needed that can handle traffic load dynamics in scenarios with sudden changes in traffic demand and dynamically distribute traffic to benefit from available resources. Trade-offs between optimality, stability and signaling overhead that are important for traffic engineering methods in the fixed Internet becomes even more critical in a dynamic ambient environment.

  • 42.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Hagsand, Olof
    Marsh, Ian
    RISE - Research Institutes of Sweden, ICT, SICS.
    TCP over High Speed Variable Capacity Links: A Simulation Study for Bandwidth Allocation2002Conference paper (Refereed)
  • 43.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Kreuger, Per
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    A case for resource management in IPTV distribution2008Conference paper (Refereed)
  • 44.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Kreuger, Per
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Resource Management for IPTV distribution2009In: ERCIM News, Vol. 77Article in journal (Other academic)
  • 45.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Marsh, Ian
    RISE - Research Institutes of Sweden, ICT, SICS.
    DTMsim - DTM channel simulation in ns2001Report (Other academic)
    Abstract [en]

    Dynamic Transfer Mode (DTM) is a ring based MAN technology that provides a channel abstraction with a dynamically adjustable capacity. TCP is a reliable end to end transport protocol capable of adjusting its rate. The primary goal of this work is investigate the coupling of dynamically allocating bandwidth to TCP flows with the affect this has on the congestion control mechanism of TCP. In particular we wanted to find scenerios where this scheme does not work, where either all the link capacity is allocated to TCP or congestion collapse occurs and no capacity is allocated to TCP. We have created a simulation environment using ns-2 to investigate TCP over networks which have a variable capacity link. We begin with a single TCP Tahoe flow over a fixed bandwidth link and progressively add more complexity to understand the behaviour of dynamically adjusting link capacity to TCP and vice versa.

  • 46.
    Abrahamsson, Henrik
    et al.
    RISE, Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Nordmark, Mattias
    Program Popularity and Viewer Behaviour in a Large TV-on-Demand System2012Conference paper (Refereed)
  • 47.
    Abrahamsson, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Svenska institutet för konserveringsforskning.
    Effect of various chemicals on production of toxin by Clostridium botulinum, type E1964Report (Refereed)
  • 48.
    Abrahamsson, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Svenska institutet för konserveringsforskning.
    Hållbarhet och kvalitet hos färska jordgubbar : en litteraturstudie1962Report (Refereed)
  • 49.
    Abrahamsson, K
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Svenska institutet för konserveringsforskning.
    Strålpastörisering av livsmedel : studievistelse i USA den 4/7-21/12 19621963Report (Refereed)
  • 50.
    Abrahamsson, K.
    SIK – Svenska institutet för konserveringsforskning.
    Studier över inverkan av olika kemikalier på toxinproduktionen hos Clostridium Botulinum typ E1964In: Nordisk Hygienisk Tidskrift, Vol. 45, no 1, p. 49-58Article in journal (Other academic)
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