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  • 201. Abdulle, A.
    et al.
    Engquist, Björn
    Mathematics Department, University of Texas at Austin.
    Finite element heterogeneous multiscale methods with near optimal computational complexity2007Ingår i: Multiscale Modeling & simulation, ISSN 1540-3459, E-ISSN 1540-3467, Vol. 6, nr 4, 1059-1084 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper is concerned with a numerical method for multiscale elliptic problems. Using the framework of the heterogeneous multiscale methods (HMM), we propose a micro-macro approach which combines the finite element method (FEM) for the macroscopic solver and the pseudospectral method for the microsolver. Unlike the micro-macromethods based on the standard FEM proposed so far, in the HMM we obtain, for periodic homogenization problems, a method that (slow) variable.

  • 202.
    Abedan Kondori, Farid
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Yousefi, Shahrouz
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Liu, Li
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Li, Haibo
    KTH Royal Institute of Technology, Department of Media Technology and Interaction Design.
    Head operated electric wheelchair2014Ingår i: IEEE Southwest Symposium on Image Analysis and Interpretation (SSIAI 2014), IEEE , 2014, 53-56 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Currently, the most common way to control an electric wheelchair is to use joystick. However, there are some individuals unable to operate joystick-driven electric wheelchairs due to sever physical disabilities, like quadriplegia patients. This paper proposes a novel head pose estimation method to assist such patients. Head motion parameters are employed to control and drive an electric wheelchair. We introduce a direct method for estimating user head motion, based on a sequence of range images captured by Kinect. In this work, we derive new version of the optical flow constraint equation for range images. We show how the new equation can be used to estimate head motion directly. Experimental results reveal that the proposed system works with high accuracy in real-time. We also show simulation results for navigating the electric wheelchair by recovering user head motion.

  • 203. Abedin, Md Reaz Ashraful
    et al.
    Bensch, Suna
    Hellström, Thomas
    Self-supervised language grounding by active sensing combined with Internet acquired images and text2017Ingår i: Proceedings of the Fourth International Workshop on Recognition and Action for Scene Understanding (REACTS2017), 2017, 71-83 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    For natural and efficient verbal communication between a robot and humans, the robot should be able to learn names and appearances of new objects it encounters. In this paper we present a solution combining active sensing of images with text based and image based search on the Internet. The approach allows the robot to learn both object name and how to recognise similar objects in the future, all self-supervised without human assistance. One part of the solution is a novel iterative method to determine the object name using image classi- fication, acquisition of images from additional viewpoints, and Internet search. In this paper, the algorithmic part of the proposed solution is presented together with evaluations using manually acquired camera images, while Internet data was acquired through direct and reverse image search with Google, Bing, and Yandex. Classification with multi-classSVM and with five different features settings were evaluated. With five object classes, the best performing classifier used a combination of Pyramid of Histogram of Visual Words (PHOW) and Pyramid of Histogram of Oriented Gradient (PHOG) features, and reached a precision of 80% and a recall of 78%.

  • 204.
    Abedin, Md. Zainal
    et al.
    University of Science and Technology Chittagong.
    Chowdhury, Abu Sayeed
    University of Science and Technology Chittagong.
    Hossain, Mohammad Shahadat
    University of Chittagong, Bangladesh.
    Andersson, Karl
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Karim, Razuan
    University of Science and Technology Chittagong.
    An Interoperable IP based WSN for Smart Irrigation Systems2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless Sensor Networks (WSN) have been highly developed which can be used in agriculture to enable optimal irrigation scheduling. Since there is an absence of widely used available methods to support effective agriculture practice in different weather conditions, WSN technology can be used to optimise irrigation in the crop fields. This paper presents architecture of an irrigation system by incorporating interoperable IP based WSN, which uses the protocol stacks and standard of the Internet of Things paradigm. The performance of fundamental issues of this network is emulated in Tmote Sky for 6LoWPAN over IEEE 802.15.4 radio link using the Contiki OS and the Cooja simulator. The simulated results of the performance of the WSN architecture presents the Round Trip Time (RTT) as well as the packet loss of different packet size. In addition, the average power consumption and the radio duty cycle of the sensors are studied. This will facilitate the deployment of a scalable and interoperable multi hop WSN, positioning of border router and to manage power consumption of the sensors.

  • 205.
    Abedin, Md. Zainal
    et al.
    University of Science and Technology, Chittagong.
    Paul, Sukanta
    University of Science and Technology, Chittagong.
    Akhter, Sharmin
    University of Science and Technology, Chittagong.
    Siddiquee, Kazy Noor E Alam
    University of Science and Technology, Chittagong.
    Hossain, Mohammad Shahadat
    University of Chittagong, Bangladesh.
    Andersson, Karl
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Selection of Energy Efficient Routing Protocol for Irrigation Enabled by Wireless Sensor Networks2017Ingår i: Proceedings of 2017 IEEE 42nd Conference on Local Computer Networks Workshops, 445 Hoes Lane, P.O. Box 133, Piscataway, NJ 08855-1331, 2017, 75-81 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless Sensor Networks (WSNs) are playing remarkable contribution in real time decision making by actuating the surroundings of environment. As a consequence, the contemporary agriculture is now using WSNs technology for better crop production, such as irrigation scheduling based on moisture level data sensed by the sensors. Since WSNs are deployed in constraints environments, the life time of sensors is very crucial for normal operation of the networks. In this regard routing protocol is a prime factor for the prolonged life time of sensors. This research focuses the performances analysis of some clustering based routing protocols to select the best routing protocol. Four algorithms are considered, namely Low Energy Adaptive Clustering Hierarchy (LEACH), Threshold Sensitive Energy Efficient sensor Network (TEEN), Stable Election Protocol (SEP) and Energy Aware Multi Hop Multi Path (EAMMH). The simulation is carried out in Matlab framework by using the mathematical models of those algortihms in heterogeneous environment. The performance metrics which are considered are stability period, network lifetime, number of dead nodes per round, number of cluster heads (CH) per round, throughput and average residual energy of node. The experimental results illustrate that TEEN provides greater stable region and lifetime than the others while SEP ensures more througput.

  • 206.
    Abedini, M.
    et al.
    Department of Industrial Engineering, Iran University of Science and Technology, Tehran, Iran.
    Ahmadzadeh, Farzaneh
    Mälardalens högskola, Akademin för innovation, design och teknik, Innovation och produktrealisering.
    Noorossana, R.
    Department of Industrial Engineering, Iran University of Science and Technology, Tehran, Iran.
    Customer credit scoring using a hybrid data mining approach2016Ingår i: Kybernetes, ISSN 0368-492X, E-ISSN 1758-7883, Vol. 45, nr 10, 1576-1588 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: A crucial decision in financial services is how to classify credit or loan applicants into good and bad applicants. The purpose of this paper is to propose a four-stage hybrid data mining approach to support the decision-making process. Design/methodology/approach: The approach is inspired by the bagging ensemble learning method and proposes a new voting method, namely two-level majority voting in the last stage. First some training subsets are generated. Then some different base classifiers are tuned and afterward some ensemble methods are applied to strengthen tuned classifiers. Finally, two-level majority voting schemes help the approach to achieve more accuracy. Findings: A comparison of results shows the proposed model outperforms powerful single classifiers such as multilayer perceptron (MLP), support vector machine, logistic regression (LR). In addition, it is more accurate than ensemble learning methods such as bagging-LR or rotation forest (RF)-MLP. The model outperforms single classifiers in terms of type I and II errors; it is close to some ensemble approaches such as bagging-LR and RF-MLP but fails to outperform them in terms of type I and II errors. Moreover, majority voting in the final stage provides more reliable results. Practical implications: The study concludes the approach would be beneficial for banks, credit card companies and other credit provider organisations. Originality/value: A novel four stages hybrid approach inspired by bagging ensemble method proposed. Moreover the two-level majority voting in two different schemes in the last stage provides more accuracy. An integrated evaluation criterion for classification errors provides an enhanced insight for error comparisons.

  • 207.
    Abefelt, Fredrik
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Synchronized audio playback over WIFI and Ethernet: A proof of concept multi-room audio playback system2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Huvuduppgift med detta examensarbete har varit att utveckla ett synkroniserat ljuduppspelningssystem, vilket kan spela upp ljud samtidigt på flera enheter, enheterna är anslutna med antingen med Wi-Fi eller Ethernet. Två olika tillvägagångsätt har undersökts för att utveckla systemet, ett redan färdigt system och ett system baserat på ett ramverk med öppen källkod.

    Det utvecklade systemet kan utföra synkroniserad uppspelning på fem olika enheter och kan använda Blueetooth enheter och olika mediaspelare som ljudkälla.

  • 208. Abel, John H.
    et al.
    Drawert, Brian
    Hellander, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för beräkningsvetenskap. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Tillämpad beräkningsvetenskap.
    Petzold, Linda R.
    GillesPy: A Python package for stochastic model building and simulation2016Ingår i: IEEE Life Sciences Letters, E-ISSN 2332-7685, Vol. 2, 35-38 s.Artikel i tidskrift (Refereegranskat)
  • 209. Abela, D
    et al.
    Ritchie, H
    Ababneh, D
    Gavin, C
    Nilsson, Mats F
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Niazi, M Khalid Khan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Centrum för bildanalys.
    Carlsson, K
    Webster, WS
    The effect of drugs with ion channel-blocking activity on the early embryonic rat heart2010Ingår i: Birth defects research. Part B. Developmental and reproductice toxicology, ISSN 1542-9733, E-ISSN 1542-9741, Vol. 89, nr 5, 429-440 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigated the effects of a range of pharmaceutical drugs with ion channel-blocking activity on the heart of gestation day 13 rat embryos in vitro. The general hypothesis was that the blockade of the IKr/hERG channel, that is highly important for the normal functioning of the embryonic rat heart, would cause bradycardia and arrhythmia. Concomitant blockade of other channels was expected to modify the effects of hERG blockade. Fourteen drugs with varying degrees of specificity and affinity toward potassium, sodium, and calcium channels were tested over a range of concentrations. The rat embryos were maintained for 2 hr in culture, 1 hr to acclimatize, and 1 hr to test the effect of the drug. All the drugs caused a concentration-dependent bradycardia except nifedipine, which primarily caused a negative inotropic effect eventually stopping the heart. A number of drugs induced arrhythmias and these appeared to be related to either sodium channel blockade, which resulted in a double atrial beat for each ventricular beat, or IKr/hERG blockade, which caused irregular atrial and ventricular beats. However, it is difficult to make a precise prediction of the effect of a drug on the embryonic heart just by looking at the polypharmacological action on ion channels. The results indicate that the use of the tested drugs during pregnancy could potentially damage the embryo by causing periods of hypoxia. In general, the effects on the embryonic heart were only seen at concentrations greater than those likely to occur with normal therapeutic dosing.

  • 210.
    Abelli, Björn
    Högskolan i Borås, Institutionen Handels- och IT-högskolan.
    Directing and Enacting the Information System2007Ingår i: Advances in Information Systems Development - New Methods and Practice for the Networked Society. / [ed] W Wojtkowski, W. G. Wojtkowski, J. Zupancic, G. Magyar, G. Knapp, Springer US , 2007, 13-23 s.Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 211.
    Abelli, Björn
    Mälardalens högskola, Ekonomihögskolan.
    Directing and Enacting the Information System2006Ingår i: Advances in Information Systems Development: New Methods and Practice for the Networked Society, Volume 2, Issue PART 2, 2006, 13-23 s.Konferensbidrag (Refereegranskat)
  • 212.
    Abelli, Björn
    Mälardalens högskola, Ekonomihögskolan.
    Enacting the e-Society2006Ingår i: Proceedings of the IADIS International Conference e-Society 2006, 2006, 285-298 s.Konferensbidrag (Refereegranskat)
  • 213.
    Abelli, Björn
    Högskolan i Borås, Institutionen Handels- och IT-högskolan.
    On Stage! Playwriting, Directing and Enacting the Informing Processes2007Doktorsavhandling, monografi (Övrigt vetenskapligt)
  • 214.
    Abelli, Björn
    Mälardalens högskola, Ekonomihögskolan.
    Programmeringens grunder - med exempel i C#2004Bok (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Detta är en lärobok i grundläggande programmering. Den fokuserar på att lära ut det som är gemensamt för de flesta programmeringsspråk – de grundläggande elementen och programkonstruktionerna och hur dessa relaterar till varandra, oberoende av språket. Vilket språk programmet skrivs i måste vara underordnat den uppgift programmet skall lösa. Boken går därför igenom grunderna i strukturerad programmering och visar otaliga exempel i såväl flödesdiagram, strukturdiagram, pseudokod som i källkod. I slutet av boken finns kapitel som går igenom grunderna även i objektorienterad programmering.

    Boken tonar ner inlärningen av ett specifikt programmeringsspråk, men i slutändan måste program ändå skrivas i något språk. Exemplen är skrivna i C# som har slagit igenom som ett praktiskt programmeringsspråk på mycket kort tid och redan börjat göra sitt intåg i högskolekurser i programmering.

    I första hand är boken avsedd för nybörjare i programmering på högskolenivå, som vill lära sig programmeringens grunder.

  • 215.
    Abelli, Björn
    et al.
    Mälardalens högskola, Ekonomihögskolan.
    Révay, Péter
    Mälardalens högskola, Ekonomihögskolan.
    To Be or Not To Be Computer Based2004Ingår i: Proceedings of microCAD 2004, 2004, 1-8 s.Konferensbidrag (Refereegranskat)
  • 216.
    Abenius, Erik
    KTH, Tidigare Institutioner, Numerisk analys och datalogi, NADA.
    Time-Domain Inverse Electromagnetic Scattering using FDTD and Gradient-based Minimization2004Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The thesis addresses time-domain inverse electromagneticscattering for determining unknown characteristics of an objectfrom observations of the scattered .eld. Applications includenon-destructive characterization of media and optimization ofmaterial properties, for example the design of radar absorbingmaterials.A nother interesting application is the parameteroptimization of subcell models to avoid detailed modeling ofcomplex geometries.

    The inverse problem is formulated as an optimal controlproblem where the cost function to be minimized is thedi.erence between the estimated and observed .elds, and thecontrol parameters are the unknown object characteristics. Theproblem is solved in a deterministic gradient-basedoptimization algorithm using a parallel 2D FDTD scheme for thedirect problem.This approach is computationally intensive sincethe direct problem needs to be solved in every optimizationiteration in order to compute an estimated .eld.H ighlyaccurate analytical gradients are computed from the adjointformulation.In addition to giving better accuracy than .nitedi.erences, the analytical gradients also have the advantage ofonly requiring one direct and one adjoint problem to be solvedregardless of the number of parameters.

    When absorbing boundary conditions are used to truncate thecomputational domain, the equations are non-reversible and theentire time-history of the direct solution needs to be storedfor the gradient computation.Ho wever, using an additionaldirect simulation and a restart procedure it is possible tokeep the storage at an acceptable level.

    The inverse method has been successfully applied to a widerange of industrial problems within the European project,IMPACT (Inverse Methods for Wave Propagation Applications inTime-Domain).T he results presented here includecharacterization of layered dispersive media, determination ofparameters in subcell models for thin sheets and narrow slotsand optimization problems where the observed .eld is given bydesign objectives.

  • 217. Abenius, Erik
    et al.
    Andersson, Ulf
    Edelvik, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Eriksson, Lasse
    Ledfelt, Gunnar
    Hybrid time domain solvers for the Maxwell equations in 2D2002Ingår i: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 53, 2185-2199 s.Artikel i tidskrift (Refereegranskat)
  • 218.
    Abenius, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Edelvik, Fredrik
    Thin Sheet Modeling Using Shell Elements in the Finite-Element Time-Domain Method2006Ingår i: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 54, 28-34 s.Artikel i tidskrift (Refereegranskat)
  • 219.
    Abenius, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Johansson, Christer
    A General Approach for Time-Domain Simulation of Waveguides in 3D2004Ingår i: Proc. EMB 04, Computational Electromagnetics: Methods and Applications, Göteborg, Sweden: Department of Electromagnetics, Chalmers University of Technology , 2004, 220-226 s.Konferensbidrag (Övrigt vetenskapligt)
  • 220.
    Abenius, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Johansson, Christer
    Modeling of inhomogeneous waveguides using hybrid methods2005Manuskript (preprint) (Övrigt vetenskapligt)
  • 221.
    Abenius, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Strand, Bo
    Solving inverse electromagnetic problems using FDTD and gradient-based minimization2006Ingår i: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 68, 650-673 s.Artikel i tidskrift (Refereegranskat)
  • 222. Abenius, Erik
    et al.
    Strand, Bo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Alestra, Stephane
    Inverse Electromagnetic Scattering Using the Finite-Difference Time-Domain Method2000Ingår i: Proc. Millennium Conference on Antennas and Propagation, Noordwijk, The Netherlands: ESA Publications , 2000, 4- s.Konferensbidrag (Refereegranskat)
  • 223.
    Abensour Sellström, Gabriel
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Runefelt Tõnisson, Meidi
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Analysis of Voting Algorithms: a comparative study of the Single Transferable Vote.2012Självständigt arbete på avancerad nivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Ett valsystem är det tillvägagångssätt med vilket den politiska makten fördelas bland kandidater efter ett val. Den här uppsatsen syftar till att jämföra valsystemet "enkel överförbar röst" med två andra valsystem, genom att konstruera Java-implementationer av algoritmerna för att köra exempeldata i. På så sätt utvärderar vi möjligheten att använda systemet med "enkel överförbar röst" i svenska riksdagsval. Utöver det föreslås en alternativ version av det ursprungliga systemet "enkel överförbar röst", där modifikationer gjorts för att passa de förutsättningar som råder i Sverige. Effekterna av ett sådant byte av valsystem är inte helt klarlagda och slutsatsen är att mer forskning krävs innan det finns grund för ett definitivt omdöme.

  • 224. Aberer, André
    et al.
    Stamatakis, Alexis
    Ronquist, Fredrik
    Naturhistoriska riksmuseet, Enheten för bioinformatik och genetik.
    An efficient independence sampler for updating branches in Bayesian Markov chain Monte Carlo sampling of phylogenetic trees2016Ingår i: Systematic Biology, ISSN 1063-5157, E-ISSN 1076-836X, Vol. 65, nr 1, 161-176 s.Artikel i tidskrift (Refereegranskat)
  • 225. 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 networks2005Konferensbidrag (Refereegranskat)
    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.

  • 226. Abeywardena, D.
    et al.
    Wang, Zhan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Datorseende och robotik, CVAP. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    Dissanayake, G.
    Waslander, S. L.
    Kodagoda, S.
    Model-aided state estimation for quadrotor micro air vehicles amidst wind disturbances2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper extends the recently developed Model-Aided Visual-Inertial Fusion (MA-VIF) technique for quadrotor Micro Air Vehicles (MAV) to deal with wind disturbances. The wind effects are explicitly modelled in the quadrotor dynamic equations excluding the unobservable wind velocity component. This is achieved by a nonlinear observability of the dynamic system with wind effects. We show that using the developed model, the vehicle pose and two components of the wind velocity vector can be simultaneously estimated with a monocular camera and an inertial measurement unit. We also show that the MA-VIF is reasonably tolerant to wind disturbances, even without explicit modelling of wind effects and explain the reasons for this behaviour. Experimental results using a Vicon motion capture system are presented to demonstrate the effectiveness of the proposed method and validate our claims.

  • 227. Abeywickrama, S.
    et al.
    Furdek, Marija
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab). University of Zagreb, Faculty of Electrical Engineering and Computing, Dept. of Telecommunications, Croatia.
    Monti, Paolo
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Nag, A.
    Wong, E.
    Dual-homing based protection for enhanced network availability and resource efficiency2014Ingår i: Asia Communications and Photonics Conference, ACP, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    An approach to enhance core network survivability by utilizing dual-homing capabilities of the access network. Results reveal significant improvements in core network resource utilization and connection availability, suggesting benefits to network operators and service providers.

  • 228.
    Abghari, Shahrooz
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Kazemi, Samira
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Open Data for Anomaly Detection in Maritime Surveillance2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    This thesis investigated the potential open data as a complementary resource for Anomaly Detection (AD) in the Maritime Surveillance (MS) domain. A framework for AD was proposed based on the usage of open data sources along with other traditional sources of data. According to the proposed AD framework and the algorithms for implementing the expert rules, the Open Data Anomaly Detection System (ODADS) was developed. To evaluate the accuracy of the system, an experiment on the vessel traffic data was conducted and an accuracy of 99% was obtained for the system. There was a false negative case in the system results that decreased the accuracy. It was due to incorrect AIS data in a special situation that was not possible to be handled by the detection rules in the scope of this thesis. The validity of the results was investigated by the subject matter experts from the Swedish Coastguard. The validation results showed that the majority of the ODADS evaluated anomalies were true alarms. Moreover, a potential information gap in the closed data sources was observed during the validation process. Despite the high number of true alarms, the number of false alarms was also considerable that was mainly because of the inaccurate open data. This thesis provided insights into the open data as a complement to the common data sources in the MS domain and is concluded that using open data will improve the efficiency of the surveillance systems by increasing the accuracy and covering some unseen aspects of maritime activities.

  • 229.
    Abheeshta, Putta
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för programvaruteknik.
    Comparative Analysis of Software Development Practices across Software Organisations: India and Sweden2016Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Context. System Development Methodologies (SDM’s) have been an area of intensive research in the field of software engineering. Different software organisations adopt different development methodologies and use different development practices. The frequency of usage of development practices and acceptance factors for adoption of development methodology are crucial for software organisations. The factors of acceptance and development practices differ across geographical locations. Many challenges have been presented in the literature with respect to the mismatch of the development practices across organisations while collaborating across organisations in distributed development. There is no considerable amount of research done in context of differences across development practices and acceptance factors for adoption of a particular development methodology. Objectives. The primary objectives of the research are to find out a) differences in (i) practice usage (ii) acceptance factors such as organisational, social and cultural b) explore the reasons for the differences and also investigate consequences of such differences while collaborating, across organisations located in India and Sweden. Methods. A literature review was conducted by searching in scientific databases for identifying common agile and plan-driven development practices and acceptance theories for development methodologies. Survey was conducted across organisations located in India and Sweden to find out the usage frequency of development practices and acceptance factors. Ten interviews were conducted to investigate, reasons for differences and consequences of differences from the software practitioners from organisations located in India and Sweden. Literature evidences were used to support the results collected from interviews. Results. From the survey, organisations in India have adopted a higher frequency of plan driven practices when compared to Sweden and agile practices were adopted at higher frequency in Sweden when compared to India. The number of organisations adopting "pure agile" methodologies have been significantly higher in Sweden. There was significant differences were found across the acceptance factors such as cultural, organisational, image and career factors between India and Sweden. The factors such as cultural, social, human, business and organisational factors are responsible for such differences across development practices and acceptance factors. Challenges related to communication, coordination and control were found due to the differences, while collaborating between Indian and Sweden sites. Conclusions. The study signifies the importance of identifying the frequency of development practices and also the acceptance factors responsible for adoption of development methodologies in the software organisations. The mismatch between these practices will led to various challenges. The study draws insights into various non-technical factors such as cultural, human, organisational, business and social while collaborating between organisations. Variations across these factors will lead to many coordination, communication and control issues. Keywords: Development Practices, Agile Development, Plan Driven Development, Acceptance Factors, Global Software Development.

  • 230. Abiala, Kristina
    et al.
    Hernwall, Patrik
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Tweens konstruerar identitet online – flickors och pojkars erfarenheter av sociala medier2013Ingår i: Pedagogisk forskning i Sverige, ISSN 1401-6788, Vol. 18, nr 1-2Artikel i tidskrift (Refereegranskat)
  • 231. 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, 951-969 s.Artikel 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.

  • 232.
    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

  • 233.
    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.

  • 234.
    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.

  • 235. 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. 

  • 236.
    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.

  • 237.
    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, 19-25 s.Artikel 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.

  • 238.
    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. 

  • 239.
    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.

  • 240.
    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.

  • 241.
    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.

  • 242.
    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.

  • 243.
    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.

  • 244.
    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.

  • 245. 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, 57-65 s.Konferensbidrag (Refereegranskat)
  • 246. 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.

  • 247.
    Abrahamsson, Henrik
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Internet Traffic Management2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 248.
    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.

  • 249.
    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.

  • 250.
    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.

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