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  • 251. Abiala, Kristina
    et al.
    Hernwall, Patrik
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Tweens negotiating identity online – Swedish girls' and boys' reflections on online experiences2013Ingår i: Journal of Youth Studies, ISSN 1367-6261, E-ISSN 1469-9680, Vol. 16, nr 8, s. 951-969Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    How do Swedish tweens (10–14 years old) understand and experience the writing of their online identities? How are such intertwined identity markers as gender and age expressed and negotiated? To find some answers to these questions, participants in this study were asked to write a story about the use of online web communities on pre-prepared paper roundels with buzzwords in the margins to inspire them. Content analysis of these texts using the constant comparative method showed that the main factors determining how online communities are understood and used are the cultural age and gender of the user. Both girls and boys chat online, but girls more often create blogs while boys more often play games. Gender was increasingly emphasised with age; but whereas boys aged 14 described themselves as sexually active and even users of pornography, girls of the same age described themselves as shocked and repelled by pornography and fearful of sexual threats. In this investigation an intersectionalist frame of reference is used to elucidate the intertwined power differentials and identity markers of the users' peer group situation.

  • 252.
    Abid, Muhammad Zeeshan
    KTH, Skolan för informations- och kommunikationsteknik (ICT). Technische Universität Braunschweig.
    A Multi-leader Approach to Byzantine Fault Tolerance: Achieving Higher Throughput Using Concurrent Consensus2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Byzantine Fault Tolerant protocols are complicated and hard to implement.Today’s software industry is reluctant to adopt these protocols because of thehigh overhead of message exchange in the agreement phase and the high resourceconsumption necessary to tolerate faults (as 3 f + 1 replicas are required totolerate f faults). Moreover, total ordering of messages is needed by mostclassical protocols to provide strong consistency in both agreement and executionphases. Research has improved throughput of the execution phase by introducingconcurrency using modern multicore infrastructures in recent years. However,improvements to the agreement phase remains an open area.

    Byzantine Fault Tolerant systems use State Machine Replication to tolerate awide range of faults. The approach uses leader based consensus algorithms for thedeterministic execution of service on all replicas to make sure all correct replicasreach same state. For this purpose, several algorithms have been proposed toprovide total ordering of messages through an elected leader. Usually, a singleleader is considered to be a bottleneck as it cannot provide the desired throughputfor real-time software services. In order to achieve a higher throughput there is aneed for a solution which can execute multiple consensus rounds concurrently.

    We present a solution that enables multiple consensus rounds in parallel bychoosing multiple leaders. By enabling concurrent consensus, our approach canexecute several requests in parallel. In our approach we incorporate applicationspecific knowledge to split the total order of events into multiple partial orderswhich are causally consistent in order to ensure safety. Furthermore, a dependencycheck is required for every client request before it is assigned to a particular leaderfor agreement. This methodology relies on optimistic prediction of dependenciesto provide higher throughput. We also propose a solution to correct the course ofexecution without rollbacking if dependencies were wrongly predicted.

    Our evaluation shows that in normal cases this approach can achieve upto 100% higher throughput than conventional approaches for large numbers ofclients. We also show that this approach has the potential to perform better incomplex scenarios

  • 253.
    Abid, Saad Bin
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Data- och elektroteknik.
    Wei, Xian
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Data- och elektroteknik.
    Development of Software for Feature Model Rendering2006Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    This Master’s thesis is aimed at improving the management of artifacts in the context of a joint-project between Jönköping University with the SEMCO project and industrial partner, a company involved in developing software for safety components. Both have a slightly distinct interest but this project can serve both parties.

    Nowadays feature modelling is efficient way for domain analysis. The purpose of this master thesis is to analysis existing four popular feature diagrams, to find out commonalities between each of them and conclude results to give suggestions of how to use existing notation systems efficiently and according to situations.

    The developed software based on knowledge established from research analysis. Two notation systems which are suggested in research part of the thesis report are implemented in the developed software “NotationManager”. The development procedures are also described and developer choices are mentioned along with the comparisons according to the situations

    Scope of the research part as well as development is discussed. Future work for developed solution is also suggested.

  • 254.
    Abi-Haidar, Layal
    Högskolan i Skövde, Institutionen för informationsteknologi.
    Realtidsgenomsökning efter säkerhetsrisker i JavaScript-kod2015Självständigt arbete på grundnivå (kandidatexamen), 15 poäng / 22,5 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Syftet med detta arbete är att undersöka om det är möjligt att kunna i realtid undersöka kod på en webbsida för att rekommendera uppdatering av en befintlig webbläsare vid behov, utan att användarupplevelsen påverkas negativt. För att undersöka detta implementerades ett program i JavaScript. Sex olika JavaScript-bibliotek användes som testfall. Programmet söker igenom koden som finns i ett JavaScript-bibliotek och gör en rekommendation med hänsyn till några kända säkerhetsrisker och försvar mot dem. Dessutom beräknar programmet svarstiden med hjälp av klockan på klientsidan.

    Enligt Tolia, Andersen och Satyanarayanan (2006) visar undersökningar som har gjorts att användare föredrar svarstider som är under en sekund, och att svarstider som är över en sekund kan få användarna att bli missnöjda. För att användarupplevelsen inte skall påverkas negativt, bör svarstiden inte överstiga en sekund.

    Resultaten från undersökningen visar att svarstiderna inte blir tillräckligt långa för att kunna påverka användarupplevelsen negativt.

  • 255. Abolhassani, M.
    et al.
    Chan, T. -HH.
    Chen, Fei
    KTH.
    Esfandiari, H.
    Hajiaghayi, M.
    Mahini, H.
    Wu, X.
    Beating ratio 0.5 for weighted oblivious matching problems2016Ingår i: Leibniz International Proceedings in Informatics, LIPIcs, Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    We prove the first non-trivial performance ratios strictly above 0.5 for weighted versions of the oblivious matching problem. Even for the unweighted version, since Aronson, Dyer, Frieze, and Suen first proved a non-trivial ratio above 0.5 in the mid-1990s, during the next twenty years several attempts have been made to improve this ratio, until Chan, Chen, Wu and Zhao successfully achieved a significant ratio of 0.523 very recently (SODA 2014). To the best of our knowledge, our work is the first in the literature that considers the node-weighted and edge-weighted versions of the problem in arbitrary graphs (as opposed to bipartite graphs). (1) For arbitrary node weights, we prove that a weighted version of the Ranking algorithm has ratio strictly above 0.5. We have discovered a new structural property of the ranking algorithm: if a node has two unmatched neighbors at the end of algorithm, then it will still be matched even when its rank is demoted to the bottom. This property allows us to form LP constraints for both the node-weighted and the unweighted oblivious matching problems. As a result, we prove that the ratio for the node-weighted case is at least 0.501512. Interestingly via the structural property, we can also improve slightly the ratio for the unweighted case to 0.526823 (from the previous best 0.523166 in SODA 2014). (2) For a bounded number of distinct edge weights, we show that ratio strictly above 0.5 can be achieved by partitioning edges carefully according to the weights, and running the (unweighted) Ranking algorithm on each part. Our analysis is based on a new primal-dual framework known as matching coverage, in which dual feasibility is bypassed. Instead, only dual constraints corresponding to edges in an optimal matching are satisfied. Using this framework we also design and analyze an algorithm for the edge-weighted online bipartite matching problem with free disposal. We prove that for the case of bounded online degrees, the ratio is strictly above 0.5. 

  • 256.
    Aboode, Adam
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Anomaly Detection in Time Series Data Based on Holt-Winters Method2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I dagens värld ökar mängden insamlade data för varje dag som går, detta är en trend som sannolikt kommer att fortsätta. Samtidigt ökar även det potentiella värdet av denna data tack vare ständig utveckling och förbättring utav både hårdvara och mjukvara. För att utnyttja de stora mängder insamlade data till att skapa insikter, ta beslut eller träna noggranna maskininlärningsmodeller vill vi försäkra oss om att vår data är av god kvalité. Det finns många definitioner utav datakvalité, i denna rapport fokuserar vi på noggrannhetsaspekten.

    En metod som kan användas för att säkerställa att data är av god kvalité är att övervaka inkommande data och larma när anomalier påträffas. Vi föreslår därför i denna rapport en metod som, baserat på historiska data, kan detektera anomalier i tidsserier när nya värden anländer. Den föreslagna metoden består utav två delar, dels att förutsäga nästa värde i tidsserien genom Holt-Winters metod samt att jämföra residualen med en estimerad normalfördelning.

    Vi utvärderar den föreslagna metoden i två steg. Först utvärderas noggrannheten av de, utav Holt-Winters metod, förutsagda punkterna för olika storlekar på indata. I det andra steget utvärderas prestandan av anomalidetektorn när olika metoder för att estimera variansen av residualernas distribution används. Resultaten indikerar att den föreslagna metoden i de flesta fall fungerar bra för detektering utav punktanomalier i tidsserier med en trend- och säsongskomponent. I rapporten diskuteras även möjliga åtgärder vilka sannolikt skulle förbättra prestandan hos den föreslagna metoden.

  • 257.
    Abou Zliekha, M.
    et al.
    Damascus University/Faculty of Information Technology.
    Al Moubayed, Samer
    Damascus University/Faculty of Information Technology.
    Al Dakkak, O.
    Higher Institute of Applied Science and Technology (HIAST).
    Ghneim, N.
    Higher Institute of Applied Science and Technology (HIAST).
    Emotional Audio-Visual Arabic Text to Speech2006Ingår i: Proceedings of the XIV European Signal Processing Conference (EUSIPCO), Florence, Italy, 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    The goal of this paper is to present an emotional audio-visual. Text to speech system for the Arabic Language. The system is based on two entities: un emotional audio text to speech system which generates speech depending on the input text and the desired emotion type, and un emotional Visual model which generates the talking heads, by forming the corresponding visemes. The phonemes to visemes mapping, and the emotion shaping use a 3-paramertic face model, based on the Abstract Muscle Model. We have thirteen viseme models and five emotions as parameters to the face model. The TTS produces the phonemes corresponding to the input text, the speech with the suitable prosody to include the prescribed emotion. In parallel the system generates the visemes and sends the controls to the facial model to get the animation of the talking head in real time.

  • 258.
    Abraham, Mark James
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Beräkningsbiofysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Murtola, T.
    Schulz, R.
    Páll, Szilárd
    KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Smith, J. C.
    Hess, Berk
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Beräkningsbiofysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Lindahl, Erik
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Beräkningsbiofysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Gromacs: High performance molecular simulations through multi-level parallelism from laptops to supercomputers2015Ingår i: SoftwareX, ISSN 2352-7110, Vol. 1-2, s. 19-25Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    GROMACS is one of the most widely used open-source and free software codes in chemistry, used primarily for dynamical simulations of biomolecules. It provides a rich set of calculation types, preparation and analysis tools. Several advanced techniques for free-energy calculations are supported. In version 5, it reaches new performance heights, through several new and enhanced parallelization algorithms. These work on every level; SIMD registers inside cores, multithreading, heterogeneous CPU-GPU acceleration, state-of-the-art 3D domain decomposition, and ensemble-level parallelization through built-in replica exchange and the separate Copernicus framework. The latest best-in-class compressed trajectory storage format is supported.

  • 259.
    Abrahamsson, Andreas
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för beräkningsvetenskap.
    Pettersson, Rasmus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för beräkningsvetenskap.
    Smoothing of initial conditions for high order approximations in option pricing2016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this article the Finite Difference method is used to solve the Black Scholes equation. A second order and fourth order accurate scheme is implemented in space and evaluated. The scheme is then tried for different initial conditions. First the discontinuous pay off function of a European Call option is used. Due to the nonsmooth charac- teristics of the chosen initial conditions both schemes show an order of two. Next, the analytical solution to the Black Scholes is used when t=T/2. In this case, with a smooth initial condition, the fourth order scheme shows an order of four. Finally, the initial nonsmooth pay off function is modified by smoothing. Also in this case, the fourth order method shows an order of convergence of four. 

  • 260.
    Abrahamsson, Anna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik.
    Variance Adaptive Quantization and Adaptive Offset Selection in High Efficiency Video Coding2016Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Video compression uses encoding to reduce the number of bits that are used forrepresenting a video file in order to store and transmit it at a smaller size. Adecoder reconstructs the received data into a representation of the original video.Video coding standards determines how the video compression should beconducted and one of the latest standards is High Efficiency Video Coding (HEVC).One technique that can be used in the encoder is variance adaptive quantizationwhich improves the subjective quality in videos. The technique assigns lowerquantization parameter values to parts of the frame with low variance to increasequality, and vice versa. Another part of the encoder is the sample adaptive offsetfilter, which reduces pixel errors caused by the compression. In this project, thevariance adaptive quantization technique is implemented in the Ericsson researchHEVC encoder c65. Its functionality is verified by subjective evaluation. It isinvestigated if the sample adaptive offset can exploit the adjusted quantizationparameters values when reducing pixel errors to improve compression efficiency. Amodel for this purpose is developed and implemented in c65. Data indicates thatthe model can increase the error reduction in the sample adaptive offset. However,the difference in performance of the model compared to a reference encoder is notsignificant.

  • 261.
    Abrahamsson, Björn
    Linköpings universitet, Institutionen för systemteknik.
    Architectures for Multiplication in Galois Rings2004Självständigt arbete på grundnivå (yrkesexamen)Studentuppsats
    Abstract [en]

    This thesis investigates architectures for multiplying elements in Galois rings of the size 4^m, where m is an integer.

    The main question is whether known architectures for multiplying in Galois fields can be used for Galois rings also, with small modifications, and the answer to that question is that they can.

    Different representations for elements in Galois rings are also explored, and the performance of multipliers for the different representations is investigated.

  • 262.
    Abrahamsson, Charlotte
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för programvarusystem.
    Wessman, Mattias
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för programvarusystem.
    WLAN Security: IEEE 802.11b or Bluetooth - which standard provides best security methods for companies?2004Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Which security holes and security methods do IEEE 802.11b and Bluetooth offer? Which standard provides best security methods for companies? These are two interesting questions that this thesis will be about. The purpose is to give companies more information of the security aspects that come with using WLANs. An introduction to the subject of WLAN is presented in order to give an overview before the description of the two WLAN standards; IEEE 802.11b and Bluetooth. The thesis will give an overview of how IEEE 802.11b and Bluetooth works, a in depth description about the security issues of the two standards will be presented, security methods available for companies, the security flaws and what can be done in order to create a secure WLAN are all important aspects to this thesis. In order to give a guidance of which WLAN standard to choose, a comparison of the two standards with the security issues in mind, from a company's point of view is described. We will present our conclusion which entails a recommendation to companies to use Bluetooth over IEEE 802.11b, since it offers better security methods.

  • 263.
    Abrahamsson, Claes
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Videokompression och användarnytta2007Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats
    Abstract [sv]

    Digital video är ett område som expanderat kraftigt senaste åren. På grund av avancerade videokompressionsmetoder kan numera en hel långfilm rymmas på mobiltelefonen eller den handhållna videospelaren. Men hur fungerar videokompression och hur hårt kan man komprimera en viss filmsekvens med bibehållen användarnytta? I denna uppsats görs en genomgång för grunderna inom videokompression. Dess förhållande till användarnyttan undersöks genom ett experiment. I detta experiment testas tre videosekvenser komprimerade med tre olika kodekar i tre olika datahastigheter för tre olika experimentgrupper. Slutsatsen av

    denna studie är att det är svårt att hitta en exakt brytpunkt där användaren finner videokvaliteten oacceptabel. Dock kan det konstateras att den högsta datahastigheten(256 kbit/s) genererar hög användarnytta medan den lägsta datahastigheten genererar låg användarnytta. Mellanhastigheten 128 kbit/s får knappt godkänt av testpersonerna.

  • 264.
    Abrahamsson, David
    Linköpings universitet, Institutionen för datavetenskap.
    Security Enhanced Firmware Update Procedures in Embedded Systems2008Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    Many embedded systems are complex, and it is often required that the firmware in these systems are updatable by the end-user. For economical and confidentiality reasons, it is important that these systems only accept firmware approved by the firmware producer.

    This thesis work focuses on creating a security enhanced firmware update procedure that is suitable for use in embedded systems. The common elements of embedded systems are described and various candidate algorithms are compared as candidates for firmware verification. Patents are used as a base for the proposal of a security enhanced update procedure. We also use attack trees to perform a threat analysis on an update procedure.

    The results are a threat analysis of a home office router and the proposal of an update procedure. The update procedure will only accept approved firmware and prevents reversion to old, vulnerable, firmware versions. The firmware verification is performed using the hash function SHA-224 and the digital signature algorithm RSA with a key length of 2048. The selection of algorithms and key lengths mitigates the threat of brute-force and cryptanalysis attacks on the verification algorithms and is believed to be secure through 2030.

  • 265.
    Abrahamsson, Emil
    Högskolan i Gävle, Institutionen för matematik, natur- och datavetenskap.
    Digitalt arkiv2008Studentarbete andra termin, 10 poäng / 15 hpStudentuppsats
    Abstract [sv]

    Grunden för detta arbete har varit att förenkla hantering och sökning bland ritningar och förteckningar i ett ritningsarkiv. Lösningen har blivit ett webbaserat datasystem som bygger på en databas där all information lagras och är sökbar. Resultatet har blivit ett system som man oavsett var man befinner sig inom företagets nätverk ha tillgång till alla ritningar och förteckningar på ett snabbt och effektivt sätt.

  • 266. Abrahamsson, Emil
    et al.
    Forni, Timothy
    Skeppstedt, Maria
    Kvist, Maria
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Medical text simplification using synonym replacement: adapting assessment of word difficulty to a compounding language2014Ingår i: Proceedings of the 3rdWorkshop on Predicting andImproving Text Readability for Target Reader Populations(PITR) / [ed] Sandra Williams, Stroudsburg: Association for Computational Linguistics , 2014, s. 57-65Konferensbidrag (Refereegranskat)
  • 267. Abrahamsson, H
    et al.
    Hagsand, Olof
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    Marsh, Ian
    TCP over high speed variable capacity links: A simulation study for bandwidth allocation2002Konferensbidrag (Refereegranskat)
    Abstract [en]

     New optical network technologies provide opportunities for fast, controllable bandwidth management. These technologies can now explicitly provide resources to data paths, creating demand driven bandwidth reservation across networks where an applications bandwidth needs can be meet almost exactly. Dynamic synchronous Transfer Mode (DTM) is a gigabit network technology that provides channels with dynamically adjustable capacity. TCP is a reliable end-to-end transport protocol that adapts its rate to the available capacity. Both TCP and the DTM bandwidth can react to changes in the network load, creating a complex system with inter-dependent feedback mechanisms. The contribution of this work is an assessment of a bandwidth allocation scheme for TCP flows on variable capacity technologies. We have created a simulation environment using ns-2 and our results indicate that the allocation of bandwidth maximises TCP throughput for most flows, thus saving valuable capacity when compared to a scheme such as link over-provisioning. We highlight one situation where the allocation scheme might have some deficiencies against the static reservation of resources, and describe its causes. This type of situation warrants further investigation to understand how the algorithm can be modified to achieve performance similar to that of the fixed bandwidth case.

  • 268.
    Abrahamsson, Henrik
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Internet Traffic Management2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 269.
    Abrahamsson, Henrik
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Network overload avoidance by traffic engineering and content caching2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 270.
    Abrahamsson, Henrik
    RISE., Swedish ICT, SICS. School of Innovation, Design and Engineering.
    Network overload avoidance by traffic engineering and content caching2012Doktorsavhandling, monografi (Övrigt vetenskapligt)
    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.

  • 271.
    Abrahamsson, Henrik
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Traffic measurement and analysis1999Rapport (Övrigt vetenskapligt)
    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.

  • 272.
    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 Flows2003Rapport (Övrigt vetenskapligt)
    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.

  • 273.
    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 traffic2000Konferensbidrag (Refereegranskat)
  • 274.
    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.2002Konferensbidrag (Refereegranskat)
  • 275.
    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 charging2002Ingår i: 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, s. 135-144Konferensbidrag (Refereegranskat)
  • 276.
    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 Links2017Konferensbidrag (Refereegranskat)
    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.

  • 277.
    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
    Delay and Traffic Intensity Monitoring in an Operational IP Network2015Konferensbidrag (Refereegranskat)
  • 278.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science, Kista, Sweden.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Caching for IPTV distribution with time-shift2013Ingår i: 2013 International Conference on Computing, Networking and Communications, ICNC 2013, IEEE , 2013, s. 916-921Konferensbidrag (Refereegranskat)
    Abstract [en]

    Today video and TV distribution dominate Internet traffic and the increasing demand for high-bandwidth multimedia services puts pressure on Internet service providers. In this paper we simulate TV distribution with time-shift and investigate the effect of introducing a local cache close to the viewers. We study what impact TV program popularity, program set size, cache replacement policy and other factors have on the caching efficiency. The simulation results show that introducing a local cache close to the viewers significantly reduces the network load from TV-on-Demand services. By caching 4% of the program volume we can decrease the peak load during prime time by almost 50%. We also show that the TV program type and how program popularity changes over time can have a big influence on cache hit ratios and the resulting link loads

  • 279.
    Abrahamsson, Henrik
    et al.
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Björkman, Mats
    Caching for IPTV distribution with time-shift2013Konferensbidrag (Refereegranskat)
  • 280.
    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-IS2009Konferensbidrag (Refereegranskat)
  • 281.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Simulation of IPTV caching strategies2010Ingår i: Proceedings of the 2010 International Symposium on Performance Evaluation of Computer and Telecommunication Systems, 2010, s. 187-193Konferensbidrag (Refereegranskat)
    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.

  • 282.
    Abrahamsson, Henrik
    et al.
    RISE., Swedish ICT, SICS, Decisions, Networks and Analytics lab.
    Björkman, Mats
    Simulation of IPTV caching strategies2010Konferensbidrag (Refereegranskat)
    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.

  • 283.
    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 approaches2004Ingår i: Swedish National Computer Networking Workshop, 2004, 1Konferensbidrag (Refereegranskat)
    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.

  • 284.
    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 Allocation2002Konferensbidrag (Refereegranskat)
  • 285.
    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 distribution2008Konferensbidrag (Refereegranskat)
  • 286.
    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 distribution2009Ingår i: ERCIM News, Vol. 77Artikel i tidskrift (Övrigt vetenskapligt)
  • 287.
    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 ns2001Rapport (Övrigt vetenskapligt)
    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.

  • 288.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science, Kista, Sweden.
    Nordmark, Mattias
    TeliaSonera AB, Stockholm, Sweden .
    Program popularity and viewer behaviour in a large TV-on-Demand system2012Ingår i: IMC '12 Proceedings of the 2012 ACM conference on Internet measurement conference, New York: ACM , 2012, s. 199-210Konferensbidrag (Refereegranskat)
    Abstract [en]

    Today increasingly large volumes of TV and video are distributed over IP-networks and over the Internet. It is therefore essential for traffic and cache management to understand TV program popularity and access patterns in real networks.

    In this paper we study access patterns in a large TV-on-Demand system over four months. We study user behaviour and program popularity and its impact on caching. The demand varies a lot in daily and weekly cycles. There are large peaks in demand, especially on Friday and Saturday evenings, that need to be handled.

    We see that the cacheability, the share of requests that are not first-time requests, is very high. Furthermore, there is a small set of programs that account for a large fraction of the requests. We also find that the share of requests for the top most popular programs grows during prime time, and the change rate among them decreases. This is important for caching. The cache hit ratio increases during prime time when the demand is the highest, and aching makes the biggest difference when it matters most.

    We also study the popularity (in terms of number of requests and rank) of individual programs and how that changes over time. Also, we see that the type of programs offered determines what the access pattern will look like.

  • 289.
    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 System2012Konferensbidrag (Refereegranskat)
  • 290.
    Abrahamsson, Jimmy
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nätverksoptimering: Bästa möjliga tillgänglighet till lägsta möjliga länkkostnad2012Självständigt arbete på grundnivå (högskoleexamen), 5 poäng / 7,5 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Denna uppsats behandlar nätverksoptimering, med fokus på att få fram den bästa möjliga tillgängligheten till lägsta möjliga kostnad, i form av länkar. I studien tas en teoretiskt grundad hypotes om en metod fram för att lösa detta problemet. Samt genomförs ett test där metoden appliceras på ett studieobjekt för att bekräfta huruvida metoden verkar fungerar eller inte.

    Resultatet blir slutligen en metod som genom att analysera tillgängligheten, länk redundansen samt beräkna antal oberoende vägar mellan noder i ett nätverk. Kan genom att jämföra resultat från före en förändring med resultat från efter en förändring lyfta fram de förändringar som medför förbättringar. Varpå ett nätverk kan optimeras till bästa möjliga tillgänglighet till lägsta möjliga kostnad, i form av länkar.

  • 291.
    Abrahamsson, Johan
    et al.
    Umeå universitet, Samhällsvetenskaplig fakultet, Informatik.
    Sjöberg, Robin
    Umeå universitet, Samhällsvetenskaplig fakultet, Informatik.
    E-tjänstutveckling ur ett medborgarperspektiv: Att skapa beslutsunderlag baserat på medborgarärendens lämplighet för olika kommunikationskanaler2009Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Citizens’ interaction with governments is an area with unique implications for channel management. Governments need to take the citizens perspective into further consideration in order to be successful in delivering high-quality e-services. This paper aims to determine if a categorization of citizen-initiated contacts from a citizen-centric perspective can be a valuable basis for decisions regarding e-service development. The study consisted of three steps. The first step was an examination of the existing related literature, which resulted in the uncovering of the most important aspects of citizens channel choice. The second step consisted of an elaboration of a classification based on perceived task characteristics and a subsequent matching of the categories to desirable channel characteristics. The third and final step consisted of an application of the proposed categorization on a content management system containing all citizen-initiated contacts in a Swedish municipality. The application indicated that the proposed categorization could possibly be used to guide investments in e-services towards a channel-appropriate direction.

  • 292.
    Abrahamsson, Jonas
    Högskolan i Skövde, Institutionen för datavetenskap.
    Metoder vid implementation av affärssystem: en studie om anpassning2001Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats
    Abstract [sv]

    Dagens företag är i stort behov av information. Företag som har många avdelningar behöver möjligheter för att enkelt och smidigt kunna samordna information för hela företaget. Affärssystem erbjuder denna möjlighet genom en modulbaserad konstruktion som integrerar ett företags samtliga avdelningar i ett enda system. Problem kan dock uppstå då ett valt affärssystem inte passar företagets verksamhet. En kompromiss mellan system och verksamhet måste då försöka uppnås.

    Ett affärssystem implementeras ofta i samband med en metod, vilken ger detaljerade beskrivningar för hur implementeringen ska gå till. På vilka grunder väljer företagen att arbeta efter en specifik metod då system och verksamhet behöver anpassas till varandra?

    Detta arbete bygger på en undersökning som har utförts genom en survey där fem företag har medverkat. Resultatet av undersökningen visar ett antal metoder samt presenterar orsaker till varför dessa metoder används.

  • 293.
    Abrahamsson, Lars
    Linköpings universitet, Institutionen för systemteknik.
    A portal based system for indoor environs2006Självständigt arbete på grundnivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    The purpose of this thesis is to document the development of the graphics part of an extremely pluggable game engine/lab environment for a course in advanced game programming. This thesis is one out of five, and concerns indoor, realtime computer 3D graphics. It covers state-of-the-art techniques such as GLSL - the OpenGL Shading Language - and more well known techniques such as portal based rendering.

  • 294.
    Abrahamsson, Lisa
    et al.
    Blekinge Tekniska Högskola.
    Lagerqvist, Amelie
    Blekinge Tekniska Högskola.
    Att formas och att formge: Normkritisk mönsterformgivning2015Självständigt arbete på grundnivå (kandidatexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Vårt samhälle är uppbyggt av normer som säger hur vi bör se ut, bete oss och leva. Många av dessa normer fokuserar på hur en person som man eller kvinna bör vara i förhållande till sitt kön. Könsnormer återspeglas i design och det vi formger, i produkter, möbler och byggnader. Genom ett genusspecificerat normkritiskt förhållningssätt undersöker vi hur könsnormer uppkommer i design och hur vi som formgivare kan designa normkritiskt. Med mönsterdesign som undersökande metod vill vi belysa och undersöka hur könsnormer upprepas i det vi formger, precis som ett mönster definieras av linjer och former som upprepas eller upplevs att göra det.

    Under vår undersökning framkommer det att mönster kan bidra till diskussion och ställningstagande som fungerar i flera forum. Vi undersöker hur unisex och manligt och kvinnligt kan gestaltas i mönster och hur normkritik fungerar som förhållningssätt i en designprocess.

  • 295. Abrahamsson, M.
    et al.
    Sundberg, Johan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Musikakustik.
    Subglottal pressure variation in actors’ stage speech2007Ingår i: Voice and Gender Journal for the Voice and Speech Trainers Association / [ed] Rees, M., VASTA Publishing , 2007, s. 343-347Kapitel i bok, del av antologi (Refereegranskat)
  • 296.
    Abrahamsson, Marcus
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    A platform for third-party applications on the web2013Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    A trend seen on the web today is to create a platform where externally developed applications can run inside some kind of main application. This is often done by providing an API to access data and business logic of your service and a sandbox environment in which third-party applications can run. By providing this, it is made possible for external developers to come up with new ideas based on your service. Some good examples on this are Spotify Apps, Apps on Facebook and SalesForce.com.

    Ipendo Systems AB is a company that develops a web platform for intellectual properties. Currently most things on this platform are developed by developers at Ipendo Systems AB. Some interest has though risen to enable external developers to create applications that will in some way run inside the main platform.

    In this thesis an analysis of already existing solutions has been done. These solutions were Spotify Apps and Apps on Facebook. The two have different approaches on how to enable third-party applications to run inside their own service. Facebook’s solution builds mainly on iframe embedded web pages where data access is provided through a web API. Spotify on the other hand hosts the third-party applications themselves but the applications may only consist of HTML5, CSS3 and JavaScript.

    In addition to the analysis a prototype was developed. The purpose of the prototype was to show possible ways to enable third-party applications to run inside your own service. Two solutions showing this were developed. The first one was based on Facebook’s approach with iframing of external web pages. The second was a slightly modified version of Spotify’s solution with only client-side code hosted by the main application. To safely embed the client side code in the main application a sandboxing tool for JavaScript called Caja was used.

    Of the two versions implemented in the prototype was the Iframe solution considered more ready to be utilized in a production environment than Caja. Caja could be seen as an interesting technique for the future but might not be ready to use today. The reason behind this conclusion was that Caja decreased the performance of the written JavaScript as well as adding complexity while developing the third-party applications.

  • 297.
    Abrahamsson, Peder
    Linköpings universitet, Institutionen för datavetenskap.
    Mer lättläst: Påbyggnad av ett automatiskt omskrivningsverktyg till lätt svenska2011Självständigt arbete på grundnivå (kandidatexamen), 12 poäng / 18 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Det svenska språket ska finnas tillgängligt för alla som bor och verkar i Sverige. Därförär det viktigt att det finns lättlästa alternativ för dem som har svårighet att läsa svensktext. Detta arbete bygger vidare på att visa att det är möjligt att skapa ett automatisktomskrivningsprogram som gör texter mer lättlästa. Till grund för arbetet liggerCogFLUX som är ett verktyg för automatisk omskrivning till lätt svenska. CogFLUXinnehåller funktioner för att syntaktiskt skriva om texter till mer lättläst svenska.Omskrivningarna görs med hjälp av omskrivningsregler framtagna i ett tidigare projekt.I detta arbete implementeras ytterligare omskrivningsregler och även en ny modul förhantering av synonymer. Med dessa nya regler och modulen ska arbetet undersöka omdet är det är möjligt att skapa system som ger en mer lättläst text enligt etableradeläsbarhetsmått som LIX, OVIX och Nominalkvot. Omskrivningsreglerna ochsynonymhanteraren testas på tre olika texter med en total lägnd på ungefär hundra tusenord. Arbetet visar att det går att sänka både LIX-värdet och Nominalkvoten signifikantmed hjälp av omskrivningsregler och synonymhanterare. Arbetet visar även att det finnsfler saker kvar att göra för att framställa ett riktigt bra program för automatiskomskrivning till lätt svenska.

  • 298.
    Abrahamsson, Richard
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Kay, Steven M.
    Stoica, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Estimation of the parameters of a bilinear model with applications to submarine detection and system identification2007Ingår i: Digital signal processing (Print), ISSN 1051-2004, E-ISSN 1095-4333, Vol. 17, nr 4, s. 756-773Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work we study the problem of estimating the parameters of a bilinear model describing, e.g., the amplitude modulation of extremely low frequency electromagnetic (ELFE) signatures of submarines. A similar problem arises in estimation of a nonlinear dynamic system using a Hammerstein–Wiener model, where two nonlinear static blocks surround a linear dynamic block. For these purposes a new method is derived. It is also shown in the same context that a two-stage method for parameter estimation of Hammerstein–Wiener models can be interpreted as an approximate least squares method. We also show the similarities with the problem of weighted low-rank approximation and the fact that these problems can be solved exactly in finite time using solvers for global optimization of systems of polynomials based on self dual optimization.

  • 299.
    Abrahamsson, Robin
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Berntsen, David
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Comparing modifiability of React Native and two native codebases2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Creating native mobile application on multiple platforms generate a lot of duplicate code. This thesis has evaluated if the code quality attribute modifiability improves when migrating to React Native. One Android and one iOS codebase existed for an application and a third codebase was developed with React Native. The measurements of the codebases were based on the SQMMA-model. The metrics for the model were collected with static analyzers created specifically for this project. The results created consists of graphs that show the modifiability for some specific components over time and graphs that show the stability of the platforms. These graphs show that when measuring code metrics on applications over time it is better to do this on a large codebase that has been developed for some time. When calculating a modifiability value the sum of the metrics and the average value of the metrics between files should be used and it is shown that the React Native platform seems to be more stable than native.

  • 300.
    Abrahamsson, Sofie
    et al.
    Södertörns högskola, Institutionen för kommunikation, medier och it.
    Eriksson, Emelie
    Södertörns högskola, Institutionen för kommunikation, medier och it.
    En utvärdering av synthesizern OP-1 utifrån ett användbarhetsperspektiv2010Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Denna rapport handlar om en användbarhetsutvärdering av synthesizern OP-1, utvecklad av företaget Teenage Engineering. Studien är kvalitativ och undersöker bara den omedelbara användarupplevelsen av produkten. Rapporten baseras på resultat från ett antal användbarhetstester, utförda på företaget i fråga. Användbarhetstesterna avser att undersöka hur en användare kan förstå hur OP-1:s kan användas och hur de kan förstår dess olika lägen och vidare på vilket sätt detta påverkar den initiala användarupplevelsen.

    Totalt nio av fjorton tillfrågade personer har ingått i användbarhetstesterna. Urvalsgruppen bestod av personer med tidigare, dock varierande mängd, erfarenhet av synthesizers. I den teoretiska referensramen förenas Jonas Löwgren och Erik Stoltermans brukskvalitetsteorier tillsammans med valda delar av Donald Normans ” Seven Stages of Actions as Design Aids”.

    Resultatet visar att användarna snabbt kommer igång med synthesizerns grundläggande funktioner. Samtliga användare tycker att OP-1 är estetiskt tilltalande, underhållande och uppskattar dess portabla format, med vilket de ser användningsområden i både resor och livesammanhang. Användarna anser också att de inte alltid måste förstå synthesizerns grafiska element, på display eller knappar, då detta tydliggörs efter användning av produkten. Användarna visar svårigheter med funktioner som pattern sequencer och viss redigering i tape. Vidare har de även ibland svårt att förstå i vilket mode som synthesizern befinner sig i.

    Samtliga användbarhetstester utfördes på en pre-betaversion av OP-1. Den slutgiltiga versionen av synthesizern har uppdaterats utefter resultaten från den här undersökningen.

     

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