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  • 251.
    Ahani, Ghafour
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Yuan, Di
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    On optimal proactive and retention-aware caching with user mobility2018Inngår i: 2018 IEEE 88th Vehicular Technology Conference (VTC-Fall), IEEE, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Caching popular contents at edge devices is an effective solution to alleviate the burden of the backhaul networks. Earlier investigations commonly neglected the storage cost in caching. More recently, retention-aware caching, where both the downloading cost and storage cost are accounted for, is attracting attention. Motivated by this, we address proactive and retention-aware caching problem with the presence of user mobility, optimizing the sum of the two types of costs. More precisely, a cost-optimal caching problem for vehicle-to-vehicle networks is formulated with joint consideration of the impact of the number of vehicles, cache size, storage cost, and content request probability. This is a combinatorial optimization problem. However, we derive a stream of analytical results and they together lead to an algorithm that guarantees global optimum with polynomial-time complexity. Numerical results show significant improvements in comparison to popular caching and random caching.

  • 252.
    Ahgren, P
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Stoica, P
    High-resolution frequency analysis with small data record2000Inngår i: ELECTRONICS LETTERS, ISSN 0013-5194, Vol. 36, nr 20, s. 1745-1747Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a paper published recently Samant and Shearman discuss several techniques for performing spectral analysis using short data records to overcome the problem of caller ID identification. They fail, however, to mention the nonlinear least squares (NLS) me

  • 253.
    Ahgren, Per
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Jakobsson, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    A study of doubletalk detection performance in the presence of acoustic echo path changes2006Inngår i: IEEE transactions on consumer electronics, ISSN 0098-3063, E-ISSN 1558-4127, Vol. 52, nr 2, s. 515-522Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An efficient and well-performing double-talk detection (DTD) algorithm is a vital part of a practically working acoustic echo canceller. However, recent algorithms are typically evaluated using a static time-invariant room acoustic impulse response, omitting a proper treatment of the case when the acoustic path is changing. In this work, we introduce a common framework to objectively evaluate how path changes affect the DTD performance. Via extensive numerical simulations, we conclude that the main factor in acoustic path changes affecting the DTD performance for some of the more common DTD algorithms is variations in the damping of the acoustic path.

  • 254. Ahlberg, Ragnar
    et al.
    Gustafsson, Bertil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    A note on parallel algorithms for partial differential equations1984Inngår i: Parallel Computing: 83, Amsterdam, The Netherlands: Elsevier Science , 1984, s. 93-98Konferansepaper (Fagfellevurdert)
  • 255.
    Ahlbom, Daniel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Quadratic Programming Modelsin Strategic Sourcing Optimization2017Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Strategic sourcing allows for optimizing purchases on a large scale.Depending on the requirements of the client and the offers provided forthem, finding an optimal or even a near-optimal solution can become computationally hard. Mixed integer programming (MIP), where theproblem is modeled as a set of linear expressions with an objectivefunction for which an optimal solution results in a minimum objectivevalue, is particularly suitable for finding competitive results. However, given the research and improvements continually being made for quadratic programming (QP), which allows for objective functions with quadratic expressions as well, comparing runtimes and objective values for finding optimal and approximate solutions is advised: for hard problems, applying the correct methods may decrease runtimes by severalorders of magnitude. In this report, comparisons between MIP and QPmodels used in four different problems with three different solverswere made, measuring both optimization and approximation performance interms of runtimes and objective values. Experiments showed that while QP holds an advantage over MIP in some cases, it is not consistentlyefficient enough to provide a significant improvement in comparison with, for example, using a different solver.

  • 256.
    Ahlén, Oscar Ahlén
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Klassificering av läkemedelshandlingar med hjälp av maskininlärning2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Handlingar kopplade till processer för godkännande och övervakning av läkemedel är mycket centrala dokument för läkemedelsmyndigheters dagliga arbete. Att ersätta manuell hantering av dessa handlingar med maskinella klassificeringssystem är en tänkbar metod för att effektivisera och kvalitetssäkra denna verksamhet. I detta arbete undersöktes möjligheten att klassificera 4750 utvalda handlingar från 10 kategorier med maskininlärning genom ett pilotprojekt på Läkemedelsverket. Maskininlärningsalgoritmer i fokus var Naive Bayes (NB), K-Nearest Neighbors (K-NN) och Support Vector Machines (SVM) och deras prestanda tillsammans med komplexitetsreducering av utvald data utvärderades. Resultatet visade på en generellt hög och jämförbar klassificeringsprestanda mellan algoritmerna där SVM hade en högsta träffsäkerhet på nästan 98%. Dessa höga siffror förklarades av en hög grad av separation i träningsdata och en större mängd handlingar och kategorier behöver utvärderas i framtida försök. Resultatet indikerar ändå på att utförligare experiment och potentiell applicering av maskininlärning mot denna domän är mycket lovande.

  • 257. Ahlford, Marianne
    et al.
    Andersson, Martin
    Blomquist, Hanna
    Ekström, Magnus
    Ericsson, Lars
    Gumbel, Johannes
    Holmgren, Anna
    Holmberg, Petter
    Kia, Leonard
    Lindström, Anton
    Lyrberg, Magnus
    Mahmoudi, Shaman
    Nolin, Bengt
    Sundien, Jesper
    Wallentin, Henrik
    Gällmo, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Datorteknik.
    Hessel, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Datorteknik.
    Mokrushin, Leonid
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Datorteknik.
    Pettersson, Paul
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Datorteknik.
    Uppsala Underdogs - A Robot Soccer Project2006Rapport (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    In this paper, we describe the four-legged soccer team Uppsala Underdogs developed by a group of 4th year computer science students at Uppsala University during the fall of 2004. The project is based on the experience from two similar previous projects. This year the emphasis of the project has been on distribution of data and on support for evaluation and reconfiguration of strategies. To support data distribution, a middleware has been developed, which implements a replication algorithm and provides a clean interface for the other software modules (or behaviors). To enable easy reconfiguration of strategies, an automata-based graphical description language has been developed, which can be compiled into code that uses the database and the lower level modules, such as tactics and positioning, to make decisions and control the robot. In addition, a graphical simulator has been developed in which the strategies can be evaluated.

  • 258.
    Ahlgren, Bengt
    et al.
    SICS.
    Björkman, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    The applicability of integrated layer processing1998Inngår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 16, nr 3, s. 317-331Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we review previous work on the applicability and performance of integrated layer processing (ILP). ILP has been shown to clearly improve computer communication performance when integrating simple data manipulation functions, but the situati

  • 259.
    Ahlgren, Bengt
    et al.
    SICS .
    Björkman, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Towards predictable ILP performance controlling communication buffer cache effects1996Inngår i: Australian Computer Journal, ISSN 0004-8917, Vol. 28, nr 2, s. 66-71Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cache memory behaviour is becoming more and more important as the speed of CPUs is increasing faster than the speed of memories. The operation of caches are statistical which means that the system level performance becomes unpredictable. In this paper we

  • 260.
    Ahlgren, Bengt
    et al.
    SICS.
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Moldeklev, Kjersti
    Telenor Research.
    Increasing communication performance with a minimal-copy data path supporting ILP and ALF1996Inngår i: Journal of High Speed Networks, ISSN 0926-6801, E-ISSN 1875-8940, Vol. 5, nr 2, s. 203-214Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many current implementations of communication subsystems on workstation class computers transfer communication data to and from primary memory several times. This is due to software copying between user and operating system address spaces, presentation la

  • 261. Ahlgren, Bengt
    et al.
    Hidell, Markus
    Ngai, Edith C.-H.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Internet of Things for smart cities: Interoperability and open data2016Inngår i: IEEE Internet Computing, ISSN 1089-7801, E-ISSN 1941-0131, Vol. 20, nr 6, s. 52-56Artikkel i tidsskrift (Fagfellevurdert)
  • 262.
    Ahlgren, Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Resursoptimering för restauranger2018Independent thesis Basic level (degree of Bachelor), 20 poäng / 30 hpOppgave
    Abstract [en]

    An optimization of reservation systems for tables in the restaurant industry. The optimization is aimed at maximizing the number of guests as well as placing guests at the optimal tables based on the prevailing conditions.

  • 263.
    Ahlkrona, Josefin
    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, Numerisk analys.
    Computational Ice Sheet Dynamics: Error control and efficiency2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Ice sheets, such as the Greenland Ice Sheet or Antarctic Ice Sheet, have a fundamental impact on landscape formation, the global climate system, and on sea level rise. The slow, creeping flow of ice can be represented by a non-linear version of the Stokes equations, which treat ice as a non-Newtonian, viscous fluid. Large spatial domains combined with long time spans and complexities such as a non-linear rheology, make ice sheet simulations computationally challenging. The topic of this thesis is the efficiency and error control of large simulations, both in the sense of mathematical modelling and numerical algorithms. In the first part of the thesis, approximative models based on perturbation expansions are studied. Due to a thick boundary layer near the ice surface, some classical assumptions are inaccurate and the higher order model called the Second Order Shallow Ice Approximation (SOSIA) yields large errors. In the second part of the thesis, the Ice Sheet Coupled Approximation Level (ISCAL) method is developed and implemented into the finite element ice sheet model Elmer/Ice. The ISCAL method combines the Shallow Ice Approximation (SIA) and Shelfy Stream Approximation (SSA) with the full Stokes model, such that the Stokes equations are only solved in areas where both the SIA and SSA is inaccurate. Where and when the SIA and SSA is applicable is decided automatically and dynamically based on estimates of the modeling error. The ISCAL method provides a significant speed-up compared to the Stokes model. The third contribution of this thesis is the introduction of Radial Basis Function (RBF) methods in glaciology. Advantages of RBF methods in comparison to finite element methods or finite difference methods are demonstrated.

    Delarbeid
    1. A numerical study of scaling relations for non-Newtonian thin-film flows with applications in ice sheet modelling
    Åpne denne publikasjonen i ny fane eller vindu >>A numerical study of scaling relations for non-Newtonian thin-film flows with applications in ice sheet modelling
    2013 (engelsk)Inngår i: Quarterly Journal of Mechanics and Applied Mathematics, ISSN 0033-5614, E-ISSN 1464-3855, Vol. 66, s. 417-435Artikkel i tidsskrift (Fagfellevurdert) Published
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-205727 (URN)10.1093/qjmam/hbt009 (DOI)000327457200001 ()
    Prosjekter
    eSSENCE
    Tilgjengelig fra: 2013-08-09 Laget: 2013-08-22 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    2. Accuracy of the zeroth- and second-order shallow-ice approximation: numerical and theoretical results
    Åpne denne publikasjonen i ny fane eller vindu >>Accuracy of the zeroth- and second-order shallow-ice approximation: numerical and theoretical results
    2013 (engelsk)Inngår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 6, s. 2135-2152Artikkel i tidsskrift (Fagfellevurdert) Published
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-213571 (URN)10.5194/gmd-6-2135-2013 (DOI)000329050500017 ()
    Prosjekter
    eSSENCE
    Tilgjengelig fra: 2013-12-19 Laget: 2013-12-28 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    3. Dynamically coupling the non-linear Stokes equations with the shallow ice approximation in glaciology: Description and first applications of the ISCAL method
    Åpne denne publikasjonen i ny fane eller vindu >>Dynamically coupling the non-linear Stokes equations with the shallow ice approximation in glaciology: Description and first applications of the ISCAL method
    2016 (engelsk)Inngår i: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 308, s. 1-19Artikkel i tidsskrift (Fagfellevurdert) Published
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-269822 (URN)10.1016/j.jcp.2015.12.025 (DOI)000369086700001 ()
    Prosjekter
    eSSENCE
    Tilgjengelig fra: 2015-12-17 Laget: 2015-12-18 Sist oppdatert: 2017-12-01bibliografisk kontrollert
    4. The ISCAL method and the grounding line: Combining the Stokes equations with the Shallow Ice Approximation and Shelfy Stream Approximation
    Åpne denne publikasjonen i ny fane eller vindu >>The ISCAL method and the grounding line: Combining the Stokes equations with the Shallow Ice Approximation and Shelfy Stream Approximation
    2016 (engelsk)Rapport (Annet vitenskapelig)
    Serie
    Technical report / Department of Information Technology, Uppsala University, ISSN 1404-3203 ; 2016-006
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-283438 (URN)
    Prosjekter
    eSSENCE
    Tilgjengelig fra: 2016-04-19 Laget: 2016-04-13 Sist oppdatert: 2016-05-16bibliografisk kontrollert
    5. A meshfree approach to non-Newtonian free surface ice flow: Application to the Haut Glacier d'Arolla
    Åpne denne publikasjonen i ny fane eller vindu >>A meshfree approach to non-Newtonian free surface ice flow: Application to the Haut Glacier d'Arolla
    2016 (engelsk)Rapport (Annet vitenskapelig)
    Serie
    Technical report / Department of Information Technology, Uppsala University, ISSN 1404-3203 ; 2016-005
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-283437 (URN)
    Prosjekter
    eSSENCE
    Tilgjengelig fra: 2016-04-19 Laget: 2016-04-13 Sist oppdatert: 2016-05-16bibliografisk kontrollert
  • 264.
    Ahlkrona, Josefin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling.
    Implementing Higher Order Dynamics into the Ice Sheet Model SICOPOLIS2011Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Ice sheet modeling is an important tool both for reconstructing past ice sheets and predicting their future evolution, but is complex and computationally costly. It involves modeling a system including the ice sheet, ice shelves and ice streams, which all have different dynamical behavior. The governing equations are non-linear, and to capture a full glacial cycle more than 100,000 years need to be simulated. To reduce the problem size, approximations of the equations are introduced. The most common approximation, the Shallow Ice Approximation (SIA), works well in the ice bulk but fails in e.g. the modeling of ice streams and the ice sheet/ice shelf coupling. In recent years more accurate models, so-called higher order models, have been constructed to address these problems. However, these models are generally constructed in an ad hoc fashion, lacking rigor. In this thesis, so-called Second Order Shallow Ice Approximation (SOSIA) equations for pressure, vertical shear stress and velocity are implemented into the ice sheet model SICOPOLIS. The SOSIA is a rigorous model derived by Baral in 1999 [3]. The numerical solution for a simple model problem is compared to an analytical solution, and benchmark experiments, comparing the model to other higher order models, are carried out. The numerical and analytical solution agree well, but the results regarding vertical shear stress and velocity differ from other models. It is concluded that there are problems with the model implemented, most likely in the treatment of the relation between stress and strain rate.

     

  • 265.
    Ahlkrona, Josefin
    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, Numerisk analys.
    The ISCAL method and the grounding line: Combining the Stokes equations with the Shallow Ice Approximation and Shelfy Stream Approximation2016Rapport (Annet vitenskapelig)
  • 266.
    Ahlkrona, Josefin
    et al.
    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, Numerisk analys.
    Kirchner, Nina
    Lötstedt, Per
    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, Numerisk analys.
    A numerical study of scaling relations for non-Newtonian thin-film flows with applications in ice sheet modelling2013Inngår i: Quarterly Journal of Mechanics and Applied Mathematics, ISSN 0033-5614, E-ISSN 1464-3855, Vol. 66, s. 417-435Artikkel i tidsskrift (Fagfellevurdert)
  • 267.
    Ahlkrona, Josefin
    et al.
    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, Numerisk analys.
    Kirchner, Nina
    Lötstedt, Per
    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, Numerisk analys.
    A numerical study of the validity of Shallow Ice Approximations2012Rapport (Annet vitenskapelig)
  • 268.
    Ahlkrona, Josefin
    et al.
    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, Numerisk analys.
    Kirchner, Nina
    Lötstedt, Per
    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, Numerisk analys.
    Accuracy of the zeroth and second order shallow ice approximation: numerical and theoretical results2013Inngår i: Geoscientific Model Development Discussions, ISSN 1991-9611, E-ISSN 1991-962X, Vol. 6, s. 4281-4325Artikkel i tidsskrift (Annet vitenskapelig)
  • 269.
    Ahlkrona, Josefin
    et al.
    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, Numerisk analys.
    Kirchner, Nina
    Lötstedt, Per
    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, Numerisk analys.
    Accuracy of the zeroth- and second-order shallow-ice approximation: numerical and theoretical results2013Inngår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 6, s. 2135-2152Artikkel i tidsskrift (Fagfellevurdert)
  • 270.
    Ahlkrona, Josefin
    et al.
    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, Numerisk analys.
    Lötstedt, Per
    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, Numerisk analys.
    Kirchner, Nina
    Zwinger, Thomas
    Dynamically coupling the non-linear Stokes equations with the shallow ice approximation in glaciology: Description and first applications of the ISCAL method2016Inngår i: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 308, s. 1-19Artikkel i tidsskrift (Fagfellevurdert)
  • 271.
    Ahlkrona, Josefin
    et al.
    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, Numerisk analys.
    Shcherbakov, Victor
    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, Numerisk analys.
    A meshfree approach to non-Newtonian free surface ice flow: Application to the Haut Glacier d'Arolla2017Inngår i: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 330, s. 633-649Artikkel i tidsskrift (Fagfellevurdert)
  • 272.
    Ahlkrona, Josefin
    et al.
    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, Numerisk analys.
    Shcherbakov, Victor
    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, Numerisk analys.
    A meshfree approach to non-Newtonian free surface ice flow: Application to the Haut Glacier d'Arolla2016Rapport (Annet vitenskapelig)
  • 273.
    Ahlman, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Improving formal analysis of computerised rail traffic control systems using domain models2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    During the formal analysis of a computerized railway control system, it may be difficult to understand if a found counterexample to a requirement is a scenario which can happen in the real world or not. By putting sensible constraints on the inputs to the system, i.e. by defining a domain model for the system, some impossible scenarios are excluded from the formal analysis, which means that the formal analysis is simplified. This thesis presents a domain model for railway control systems, expressing constraints on how trains can behave in a railway network. The railway network is abstracted into a simple graph structure and the model is described in a temporal predicate logic using operators for the initial (I) and the next (X) value. The model is carefully defined in order not to introduce any unrealistic behavior.

  • 274.
    Ahlström, Marcus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Online-instrumentering på avloppsreningsverk: status idag och effekter av givarfel på reningsprocessen2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Effektiviteten av automatiserade reningsprocesser inom avloppsreningsverk beror ytterst på kvaliteten av de mätdata som fås från installerade instrument. Givarfel påverkar verkens styrning och är ofta anledningen till att olika reglerstrategier fallerar. Idag saknas standardiserade riktlinjer för hur instrumenteringsarbetet på svenska reningsverk bör organiseras vilket ger begränsade förutsättningar för reningsverken att resurseffektivt nå sina utsläppskrav. Mycket forskning har gjorts på att optimera olika reglerstrategier men instrumentens roll i verkens effektivitet har inte givits samma uppmärksamhet. Syftet med detta examensarbete har varit att undersöka hur instrumentering på reningsverk kan organiseras och struktureras för att säkerställa mätdata av god kvalitet och att undersöka effekter av givarfel på reningsprocessen.

    Inom arbetet genomfördes en litteraturstudie där instrumentering på reningsverk under-söktes. Effekter av givarfel på reningsprocessen undersöktes genom att simulera en fördenitrifikationsprocess i Benchmark Simulation Model no. 2 där bias och drift implementerades i olika givare. Simuleringar visade att positiva bias (0,10–0,50 mg/l) i en ammoniumgivare inom en kaskadreglering bidrar till att öka luftförbrukningen med cirka 4–25 %. Vidare resulterade alla typer av fel i DO-givare i den sista aeroba bassängen i en markant större påverkan på reningsprocessen än samma fel i DO-givare i någon av de tidigare aeroba bassängerna. Om den sista aeroba bassängen är designad för att hålla lägre syrehalter är DO-givaren i den bassängen den viktigaste DO-givaren att underhålla. Positiva bias (200–1 000 mg/l) i TSS-givare som används för att styra uttaget av överskottsslam bidrog till kraftiga ökningar av mängden ammonium med cirka 29–464 % i utgående vatten. Negativ drift i DO-givare visade att stora besparingar i luftningsenergi, cirka 4 %, var möjliga genom ett mer frekvent underhåll av DO-givarna.

    Huruvida ett instrument lider av ett positivt eller negativt givarfel, bias eller drift, kommer att påverka hur mycket och i vilken mån reningsprocessen påverkas. Studien av givarfel visade att effekten av ett positivt eller ett negativt fel varierade och att effekten på reningsprocessen inte var linjär. Effekten av givarfel på reningsprocessen kommer i slutändan att bero på den implementerade reglerstrategin, inställningar i regulatorerna och på den styrda processen.

  • 275.
    Ahlén, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Ahlgren, Bengt
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Grönroos, Roland
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Hjort, Klas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrostrukturteknik.
    Katardjiev, Ilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Presentation of the VINN Excellence Center for Wireless Sensor Networks (WISENET)2008Inngår i: Conference on Radio Science (RVK08), Växjö, 2008Konferansepaper (Fagfellevurdert)
  • 276. Ahmad, Fayyaz
    et al.
    Al-Aidarous, Eman S.
    Alrehaili, Dina A.
    Ekström, Sven-Erik
    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, Numerisk analys.
    Furci, Isabella
    Serra-Capizzano, Stefano
    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, Numerisk analys.
    Are the eigenvalues of preconditioned banded symmetric Toeplitz matrices known in almost closed form?2018Inngår i: Numerical Algorithms, ISSN 1017-1398, E-ISSN 1572-9265, Vol. 78, s. 867-893Artikkel i tidsskrift (Fagfellevurdert)
  • 277. Ahmad, Fayyaz
    et al.
    Al-Aidarous, Eman S.
    Alrehaili, Dina A.
    Ekström, Sven-Erik
    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, Numerisk analys.
    Furci, Isabella
    Serra-Capizzano, Stefano
    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, Numerisk analys.
    Are the eigenvalues of preconditioned banded symmetric Toeplitz matrices known in almost closed form?2017Rapport (Annet vitenskapelig)
  • 278. Ahmad, Fayyaz
    et al.
    Serra-Capizzano, Stefano
    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, Numerisk analys.
    Zaka Ullah, Malik
    Al-Fhaid, A. Saleh
    A family of iterative methods for solving systems of nonlinear equations having unknown multiplicity2016Inngår i: Algorithms, ISSN 1999-4893, E-ISSN 1999-4893, Vol. 9, s. 5:1-10, artikkel-id 5Artikkel i tidsskrift (Fagfellevurdert)
  • 279. Ahmad, Fayyaz
    et al.
    Soleymani, Fazlollah
    Khaksar Haghani, Farhad
    Serra-Capizzano, Stefano
    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, Numerisk analys.
    Higher order derivative-free iterative methods with and without memory for systems of nonlinear equations2017Inngår i: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 314, s. 199-211Artikkel i tidsskrift (Fagfellevurdert)
  • 280.
    Ahmad, Tanvir
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Design and Implementation of Business Intelligence Systems2011Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The goal of this project was to investigate the limitations of current Business Intelligence System (BI System) which was needed to re-design its architecture and embed two new modules. These two modules were named as Survey Form and Statistics Report.

    The survey form has a very dynamic behavior, for example the administrator can generate different types of surveys instantly by drag drop quick functionality of the interface and he can also send that surveys to the users. The user will give the answers of survey questions and send them back to the management of the company where survey form modules helped them to analyze the answers in the form of graphs. This survey form is also providing five different types of scheduling system where administrator can schedule their surveys in five different ways like Once, weekly, Monthly, Quarterly and Yearly.

    Statistics module has different behaviors. It implemented four different types of reports which are inter-related with each other. These four reports were named as financial report, human resource report, project overview and company overview. The finance report was responsible that it will show the revenue amount and source, from where the company generated this revenue. The second report was belonged to human resource department which was responsible for generating the overall situation of the employees and their projects. For example how many are on holidays, idle, working and going to be free soon. The third report was representing the projects overview of all the projects. This report is responsible for checking the status of all projects and show them in bar char who will show the management that how many projects are completed, going to start or delay and going to finish soon.

    The fourth and final report was responsible for generating report for the overall company status. This project has been completed successfully. The design, architecture and, implementation of intelligent Survey Form and Statics modules have been implemented and working successfully.

  • 281.
    Åhman, Alexander
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Resurseffektivt bussprotokoll över RS-4852015Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
    Abstract [en]

    This report describes the design and implementation of a multi-master, packet based protocol for small and tiny microcontrollers where resources are limited. The protocol was named "Tiny Controller Network" or TCN for short. The protocol is meant mainly as a control bus for automation and sensor acquisition applications but due to its flexibility can also be used for other purposes as well. It borrows some of its functionality and design ideas from the well known CAN bus and Modbus but also has a number of major differences like the use of standard hardware and time synchronisation. One of the key aspects during the design was the use of very little system resources and common on-chip hardware peripherals like a UART. No special hardware resources are needed, except for the support for 9 bit bytes in the UART, also known as "Multi Processor Communication Mode". The report also describes the serial communication standards RS-232, RS-422 and RS-485 in order for the reader to gain better understanding of the different properties they have and why RS-485 was chosen as the physical layer for the protocol. Another topic that also is described is the different bus topologies and ways of termination and how they affect the performance of the bus. It also describes the simplified time synchronisation support that was included in the protocol. During the development, microcontrollers from Atmel's AVR family of 8 bit microcontrollers was used, more specifically the ATmega16. The implementation of the protocol was made for these microcontrollers in the C programming language. Also two hardware interfaces was developed for connecting a microcontroller to the TCN bus, one minimalistic and one with galvanic isolation between the bus and microcontroller.

  • 282. Ahmed, Laeeq
    et al.
    Georgiev, Valentin
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Capuccini, Marco
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Tillämpad beräkningsvetenskap.
    Toor, Salman
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Tillämpad beräkningsvetenskap.
    Schaal, Wesley
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Laure, Erwin
    Spjuth, Ola
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaceutisk biovetenskap.
    Efficient iterative virtual screening with Apache Spark and conformal prediction2018Inngår i: Journal of Cheminformatics, ISSN 1758-2946, E-ISSN 1758-2946, Vol. 10, artikkel-id 8Artikkel i tidsskrift (Fagfellevurdert)
  • 283. Ahmed-Ali, Tarek
    et al.
    Tiels, Koen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Schoukens, Maarten
    Giri, Fouad
    Sampled-data adaptive observer for state-affine systems with uncertain output equation2019Inngår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 103, s. 96-105Artikkel i tidsskrift (Fagfellevurdert)
  • 284. Ahmed-Ali, Tarek
    et al.
    Tiels, Koen
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Schoukens, Maarten
    Giri, Fouad
    Sampled-Data Based State and Parameter Estimation for State-Affine Systems with Uncertain Output Equation2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The problem of sampled-data observer design is addressed for a class of state- and parameter-affine nonlinear systems. The main novelty in this class lies in the fact that the unknown parameters enter the output equation and the associated regressor is nonlinear in the output. Wiener systems belong to this class. The difficulty with this class of systems comes from the fact that output measurements are only available at sampling times causing the loss of the parameter-affine nature of the model (except at the sampling instants). This makes existing adaptive observers inapplicable to this class of systems. In this paper, a new sampled-data adaptive observer is designed for these systems and shown to be exponentially convergent under specific persistent excitation (PE) conditions that ensure system observability and identifiability. The new observer involves an inter-sample output predictor that is different from those in existing observers and features continuous trajectories of the state and parameter estimates.

  • 285.
    Aho, Milja
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för beräkningsvetenskap.
    Optimisation of Ad-hoc analysis of an OLAP cube using SparkSQL2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    An Online Analytical Processing (OLAP) cube is a way to represent a multidimensional database. The multidimensional database often uses a star schema and populates it with the data from a relational database. The purpose of using an OLAP cube is usually to find valuable insights in the data like trends or unexpected data and is therefore often used within Business intelligence (BI). Mondrian is a tool that handles OLAP cubes that uses the query language MultiDimensional eXpressions (MDX) and translates it to SQL queries. Apache Kylin is an engine that can be used with Apache Hadoop to create and query OLAP cubes with an SQL interface. This thesis investigates whether the engine Apache Spark running on a Hadoop cluster is suitable for analysing OLAP cubes and what performance that can be expected. The Star Schema Benchmark (SSB) has been used to provide Ad-Hoc queries and to create a large database containing over 1.2 billion rows. This database was created in a cluster in the Omicron office consisting of five worker nodes and one master node. Queries were then sent to the database using Mondrian integrated into the BI platform Pentaho. Amazon Web Services (AWS) has also been used to create clusters with 3, 6 and 15 slaves to see how the performance scales. Creating a cube in Apache Kylin on the Omicron cluster was also tried, but was not possible due to the cluster running out of memory. The results show that it took between 8.2 to 11.9 minutes to run the MDX queries on the Omicron cluster. On both the Omicron cluster and the AWS cluster, the SQL queries ran faster than the MDX queries. The AWS cluster ran the queries faster than the Omicron cluster, even though fewer nodes were used. It was also noted that the AWS cluster did not scale linearly, neither for the MDX nor the SQL queries.

  • 286.
    Aiesh, Basel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Centrum för bildanalys.
    Measurement of dispersion barriers through SEM images2015Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis digital image analysis is applied to Scanning Electron Microscope imagesof dispersion barriers to measure specific properties. The thin barriers are used asprotection for paperboard packaging and are made of polymers and fillers. The orientation, area, length and density distributions of the fillers determine the functionality and quality of the barrier. Methods built on image analysis tools are developed with the objective to measure these quantities. Input for the methods are Scanning Electron Microscope images showing the cross-section of the barriers. To make the images relevant for the methods they are preprocessed by reducing noise and distinguishing fillers from the background.

    For measuring the orientation distribution of the fillers two different methods are implemented and compared. The first one is based on a structure tensor and the other one applies a covariance matrix. The structure tensor is preferable because of its flexibility and better performance for complex images. The area and length distributions are measured by applying mathematical morphology together withsoft-clipping. The density distribution is obtained by filtering the underlying image twice with a uniform filter which creates a heat map.

    The developed methods are evaluated by applying them on fabricated binary test images with known properties. The methods are very accurate when applied on simple test images but for more complex test images with greater variation the accuracy decreases. However, for most applications the results are still on an acceptable level.

  • 287.
    Aji John, Pushpam Joseph
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Wireless Air Quality and Emission Monitoring2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    There has been an influx of air-quality systems in indoor and outdoor environments. The main purpose of these systems is to gauge the air quality with parameters known to cause harmful effects to humans. Generally, an index is drawn by using these parameters to indicate the scale of pollution. Existing work in outdoor air quality systems spans across community driven sensing, mobile sensing, and city or nationally supported sensing. The large body of related work appears fragmented, and has not shown to be explored in a cradle to grave fashion. This thesis explores an integrated system built using wireless sensor network for measuring air quality in the city of Uppsala, Sweden. An in-depth study was performed to evaluate the operational performance of the system, assess the quality of data, comparison with reference monitoring stations, and analysis to study patterns.

  • 288.
    Akbarian Tari, Saman
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Svensson, Therése
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Investigation of a method to extend the use of output data from Scania's Hardware-In-the-Loop simulations: Development of database and search algorithm2014Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    In the automotive industry, Hardware-In-the-Loop (HIL) laboratories are used for testing vehicle functions and systems. Swedish heavy truck manufacturer Scania recently upgraded its HIL lab resulting in an opportunity to save all data generated by simulations in the HIL lab for post analysis. Thus, Scania wished to investigate the possibility to extend the use of output data by examining a new test method. The new test method was intended to be used for disclosing a type of error that had not been possible to detect prior to the upgraded HIL lab. The proposed test method was to store tests in a database and to run the tests upon output data generated in the HIL lab. The tests which were to be stored in the database existed as scripts written in the programming language Python. In order to insert tests into the database the data had to be extracted from the Python test scripts. The investigation showed the database test method to be feasible in small scale for some test scripts but the results also indicated weaknesses with the method’s setup. Insertion of data, extracted from test scripts, into a relational database showed to be problematic as the data was highly heterogeneous and did not fit easily into relational tables. For future implementations it is suggested that the method incorporates other information sources complementing the test scripts.

  • 289.
    Akrami, Nazar
    et al.
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Shrestha, Amendra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Berggren, Mathias
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Kaati, Lisa
    Swedish Defense Research Agency.
    Obaidi, Milan
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Cohen, Katie
    Swedish Defense Research Agency.
    Assessment of risk in written communication: Introducing the Profile Risk Assessment Tool (PRAT)2018Rapport (Annet vitenskapelig)
  • 290.
    Aksoy, Ozan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Synchronization Techniques in Object Oriented Software Development Environments: Bringing a Synchronized State among Model and Code Components in Xtext Framework2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Code Synchronization is the process to achieve an equalized state among code domains. However, the equalization process is not clearly defined. An equal state can be achieved in various forms, such as destroying all irrelevant code parts, or just letting them exist without including them in the synchronization process. For this reason, a synchronization process is depended on its synchronization behavior. This behavior is the characteristics of the process. Additionally, conditions of a synchronization process have an impact on the realization of the behavior. Behavior can only be realized if the conditions of compared states, environment variables, and abilities are configured in support of the behavior. Thus, it can be said that synchronization behavior is both the analyzer and the decision maker of a synchronization process.When a synchronization process consists of a singular synchronization analysis and implementation process for two or more code bodies, then this can also be called a synchronization attempt. A synchronization attempt is analyzed under the provided synchronization behavior in limited, expected and exceptional conditions. Though this analysis, any synchronization attempt can be concluded in the synchronization behavioral expectations.It was observed that a new synchronization theory is required to overcome the needs for the synchronization mechanisms. For this reason, synchronization as aconcept has been researched and two contributions are generated. One of these is to establish a start point for synchronization studies, which is defined in nature of synchronization. Secondly, by using the findings from nature of synchronization, expected behaviors during synchronization have been analyzed as functional calculations. These functional calculation processes have been classified and they are documented for every classified case. Additionally, a methodology for analysis and design of synchronization mechanisms has been provided. Later, this is used on Xtext Framework.This research is conducted for a double degree master program in Computer Science in Uppsala University and Software Engineering in Tongji University. The project is conducted in BMW ConnectedDrive Laboratories, Shanghai, China. It is supervised by Uppsala University, Tongji University, and Shanghai based BMW China Connected Drive Research Laboratory. It is aimed to satisfy the academic research needs of BMW AG.

  • 291.
    Aksu, Erdem
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Large Scale Multimedia Messaging Service Center with Optimized Database Implementation2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The standardization forum 3GPP has specified Multimedia Messaging Service (MMS) standard including an MMS Relay-Server that allows users to send and receive messages including multimedia contents like text, images, audio and video. A large scale Multimedia Message Service Relay-Server implementation needs an efficient database solution. The database should be able to support storage and manipulation of data for millions of transactions. Consistency and availability should be ensured under heavy traffic load to prevent data losses and service delays. In this thesis, I present the implementation and extended evaluation of a store and forward mechanism for messages kept in MMS Server and I propose a solution to use Berkeley DB as a back-end to Mnesia DBMS to achieve higher storage efficiency.  I show that it is feasible to replace database back-end of Mnesia with Berkeley DB while keeping transparency to application level and having an efficient message store in terms of higher throughput under heavy traffic.

  • 292.
    Akujuaobi, Timothy
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Streaming Explanograms: Networking for Real-Time Wireless Collaboration2008Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The project goal is to implement a client program and test server to supportstreaming collaborative interaction using state of the art PDA and Bluetooth pen technologies. The project builds on an existing prototype solution, porting it to work on the Nokia 770, extending the functionality and conducting field tests. The program is a Bluetooth Service provider and relays streaming data from a Maxell Digital Pen to a server. The project also evaluates the tradeoffs associated with using TCP against UDP transport protocols for data traffic.

  • 293.
    Al Hinai, Abdullah Hamed
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    A Performance Comparison of SQL and NoSQL Databases for Large Scale Analysis of Persistent Logs2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Recently, non-relational database systems known as NoSQL have emerged as alternative platforms to store, load and analyze Big Data. Most NoSQL systems, such as MongoDB, Redis, HBase, and Cassandra sacrifice consistency for scalability which means that users may not be able to retrieve the latest changes in the data but can execute faster queries. Alternatively, these systems provide what is known as eventual data consistency. Similarly, relational database systems allow relaxed levels of consistency to obtain performance improvements. In this master thesis project previous performance and scalability benchmarking experiments are reproduced and extended to two new popular state-of-the-art NoSQL database systems: Cassandra and Redis. Additionally, a relational database system not used in previous research was tested in this project, in addition to a new release of an already-tested open source relational system. The purpose of these experiments is to extend the previous evaluation to two relational systems and two non-relational database systems regardless of their data model by measuring the time needed to load and query persistent logs under different indexing and consistency settings. The results of this research show that there is no specific type of system consistently outperforming the others but the best option can vary depending on the features of the data, the type of query and the specific system.

  • 294.
    Al Nahas, Beshr
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Multichannel Communication in Contiki's Low-power IPv6 Stack2013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Vast majority of wireless appliances used in household, industry and medical field share the ISM frequency band. These devices need to coexist and thus are challenged to tolerate their mutual interference. One way of dealing with this is by using frequency hopping; where the device changes its radio channel periodically. Consequently, communications will not suffer from the same interference each time; instead, it should be fairer and more stable. This thesis investigates the aforementioned problem in the field of low power wireless sensor networks and Internet of Things where Contiki OS is used. We introduce a low-power pseudo-random frequency-hopping MAC protocol which is specifically characterized as a duty cycled asynchronous sender-initiated LPL style protocol. We illustrate two flavors of the protocol; one that does not use any dedicated channel and another which allows dedicated broadcast channels that can implement frequency-hopping as well. We implement the protocol in C for real hardware and extensively test and evaluate it in a simulated environment which runs Contiki. It proved to work with Contiki's IPv6 stack running RPL (the standardized routing protocol for low power and lossy wireless networks). We compare the performance of the implemented protocol to the singlechannel ContikiMAC with varying levels of interference. Results show a reduction down to 56% less radio-on time (1.50% vs. 3.4%) and 85% less latency (306 ms vs. 2050 ms) in the presence of noise, while keeping a good basecost in noise-free environments with 1.29% radio duty cycle when using 9 channels with no dedicated broadcast channels (vs. 0.80% for single channel) and 252 ms average latency(vs. 235 ms). Moreover, the results show that the multichannel protocol performance metrics converge to almost the same values regardless of the noise level. Therefore, it is recommended  as a good alternative to single channel ContikiMAC in real worlddeployments where noise presence is anticipated.

  • 295.
    Al Nahas, Beshr
    et al.
    Swedish Institute of Computer Science.
    Duquennoy, Simon
    Swedish Institute of Computer Science.
    Iyer, Venkatraman
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Low-Power Listening Goes Multi-Channel2014Inngår i: 2014 IEEE INTERNATIONAL CONFERENCE ON DISTRIBUTED COMPUTING IN SENSOR SYSTEMS (IEEE DCOSS 2014), 2014, s. 2-9Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Exploiting multiple radio channels for communicationhas been long known as a practical way to mitigateinterference in wireless settings. In Wireless Sensor Networks,however, multichannel solutions have not reached their fullpotential: the MAC layers included in TinyOS or the ContikiOS for example are mostly single-channel. The literature offersa number of interesting solutions, but experimental results wereoften too few to build confidence. We propose a practical extensionof low-power listening, MiCMAC, that performs channel hopping,operates in a distributed way, and is independent of upper layersof the protocol stack. The above properties make it easy todeploy in a variety of scenarios, without any extra configuration/scheduling/channelselection hassle. We implement our solutionin Contiki and evaluate it in a 97-node testbed while runninga complete, out-of-the-box low-power IPv6 communication stack(UDP/RPL/6LoWPAN). Our experimental results demonstrateincreased resilience to emulated WiFi interference (e.g., data yieldkept above 90% when ContikiMAC drops in the 40% range). In noiseless environments, MiCMAC keeps the overhead low incomparison to ContikiMAC, achieving performance as high as 99% data yield along with sub-percent duty cycle and sub-secondlatency for a 1-minute inter-packet interval data collection.

  • 296.
    Alabi, Derrick
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Energy-Aware Task Scheduling in Contiki2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Applications for the Internet of Things often run on devices that have very limited energy capacity. Energy harvesting can offset this inherent weakness of these devices by extracting energy from the environment. Energy harvesting increases the total energy available to a device, but efficient energy consumption is still important to maximize the availability of the device. Energy-aware task scheduling is a way to efficiently consume energy in an energy constrained device with energy harvesting capabilities to extend the device's availability. In this thesis, prediction of future incoming harvest energy is combined with hard real-time and reward-based weakly-hard real-time task scheduling schemes to achieve efficient energy usage. Linear regression and artificial neural networks are evaluated individually on their ability to predict future energy harvests. The artificial neural network used contains a single hidden layer and is evaluated with ReLU, Leaky ReLU ,and sine as activation functions. The performance of linear regression and the artificial neural network with varying activation functions and number of hidden nodes are tested and compared. Linear regression is shown to be a sufficient means of predicting future energy harvests. A hard real-time and a reward-based weakly-hard real-time task scheduling scheme are also presented and compared. The experimental results show that the hard real-time scheme can extend the life of the device compared to a non-energy-aware scheduler, but the weakly-hard real-time scheme will allow the device to function indefinitely.

  • 297.
    Alborghetti Londero, Afonso
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    A Cut-Cell Implementation of the Finite Element Method in deal.ii2015Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
    Abstract [en]

    The modeling of problems where the boundary changes significantly over time may become challenging as the mesh needs to be adapted constantly. In this context, computational methods where the mesh does not conform to the boundary are of great interest. This paper proposes a stabilized cut-cell approach to solve partial differential equations using unfitted meshes using the Finite Element Method. The open-source library deal.ii was used for implementation. In order to evaluate the method, three problems in two-dimensions were tested: the Poisson problem, a pure diffusion Laplace-Beltrami problem and a reaction diffusion case. Stabilization effects on the stiffness matrix were studied for the first two test cases, and the theoretical dependence of the condition number with mesh size was confirmed. In addition, an optimal stabilization parameter was defined. Optimal convergence rates were obtained for the first two test cases.

  • 298.
    Albrektsson, Robert
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Undersökning av elektroniska scorekort på golfmarknaden: Var ligger problemet för fortsatt utveckling?2010Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    This is a Master´s Thesis based on my own idea instead of that of a company. It is a survey that focuses on finding out more about which part of the development process that is blocking the establishment of electronic scorecards on the golf market. Why has it not been introduced on the market in a larger scale yet, considering the technology we possess today? This question is investigated through interviews with the Swedish Golf association, and three companies that have chosen different paths to implement an electronic scorecard. The interviews focuses on finding out what developers and the association believe to be the main problem, before taking the next step in releasing electronic scorecards on a larger scale. Another thing that has been a core in this survey is to always try to look on systems and how they were created from a usability point of view, to see and understand why systems look and function the way they do.

    The resu