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  • 1. Abdulla, Parosh Aziz
    et al.
    Högberg, Johanna
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kaati, Lisa
    Bisimulation minimization of tree automata2007In: International Journal of Foundations of Computer Science, ISSN 0129-0541, Vol. 18, no 4, 699-713 p.Article in journal (Refereed)
    Abstract [en]

    We extend an algorithm by Paige and Tarjan that solves the coarsest stable refinement problem to the domain of trees. The algorithm is used to minimize nondeterministic tree automata (NTA) with respect to bisimulation. We show that our algorithm has an overall complexity of $O(\hat{r} m \log n)$, where $\hat{r}$ is the maximum rank of any symbol in the input alphabet, m is the total size of the transition table, and n is the number of states.

  • 2. Abdulla, Parosh Aziz
    et al.
    Katti, Lisa
    Högberg, Johanna
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Bisimulation minimization of tree automata2006In: Implementation and Application of Automata : 11th International Conference, CIAA 2006, 2006, 699-713 p.Conference paper (Refereed)
    Abstract [en]

    We extend an algorithm by Paige and Tarjan that solves the coarsest stable refinement problem to the domain of trees. The algorithm is used to minimize nondeterministic tree automata (NTA) with respect to bisimulation. We show that our algorithm has an overall complexity of O ((r) over cap log n), where (r) over cap is the maximum rank of any symbol in the input alphabet, m is the total size of the transition table, and n is the number of states.

  • 3.
    Abedan Kondori, Farid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yousefi, Shahrouz
    Ostovar, Ahmad
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Liu, Li
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    A Direct Method for 3D Hand Pose Recovery2014In: 22nd International Conference on Pattern Recognition, 2014, 345-350 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel approach for performing intuitive 3D gesture-based interaction using depth data acquired by Kinect. Unlike current depth-based systems that focus only on classical gesture recognition problem, we also consider 3D gesture pose estimation for creating immersive gestural interaction. In this paper, we formulate gesture-based interaction system as a combination of two separate problems, gesture recognition and gesture pose estimation. We focus on the second problem and propose a direct method for recovering hand motion parameters. Based on the range images, a new version of optical flow constraint equation is derived, which can be utilized to directly estimate 3D hand motion without any need of imposing other constraints. Our experiments illustrate that the proposed approach performs properly in real-time with high accuracy. As a proof of concept, we demonstrate the system performance in 3D object manipulation. This application is intended to explore the system capabilities in real-time biomedical applications. Eventually, system usability test is conducted to evaluate the learnability, user experience and interaction quality in 3D interaction in comparison to 2D touch-screen interaction.

  • 4.
    Abedin, Reaz Ashraful
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Autonomous Object Category Learning for Service Robots Using Internet Resources2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the developments in the field of Artificial Intelligence (AI), robots are becoming smarter, more efficient and capable of doing more dififcult tasks than before. Recent progress in Machine Learning has revolutionized the field of AI. Rather than performing pre-programmed tasks, nowadays robots are learning things, and becoming more autonomous along the way. However, in most of the cases, robots need a certain level of human assistance to learn something. To recognize or classify daily objects is a very important skill that a service robot should possess. In this research work, we have implemented a fully autonomous object category learning system for service robots, where the robot uses internet resources to learn object categories. It gets the name of an unknown object by performing reverse image search in the internet search engines, and applying a verification strategy afterwards. Then the robot retrieves a number of images of that object from internet and use those to generate training data for learning classifiers. The implemented system is tested in actual domestic environment. The classification performance is examined against some object categories from a benchmark dataset. The system performed decently with 78:40% average accuracy on ve object categories taken from the benchmark dataset and showed promising results in real domestic scenarios. There are existing research works that deal with object category learning for robots using internet images. But those works use Human-in-the-loop models, where humans assist the robot to get the object name for using it as a search cue to retrieve training images from internet. Our implemented system eliminates the necessity of human assistance by making the task of object name determination automatic. This facilitates the whole process of learning object categories with full autonomy, which is the main contribution of this research.

  • 5. Adams, R.
    et al.
    Fincher, S.
    Pears, A.
    Börstler, Jürgen
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Bousted, J.
    Dalenius, P.
    Eken, G.
    Heyer, T.
    Jacobsson, A.
    Lindberg, V.
    Molin, B.
    Moström, J.-E.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wiggberg, M.
    What is the Word for Engineering in Swedish: Swedish Students' Conceptions of their Discipline2007Report (Other academic)
  • 6.
    Adlerborn, Björn
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Parallel Algorithms and Library Software for the Generalized Eigenvalue Problem on Distributed Memory Computer Systems2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    We present and discuss algorithms and library software for solving the generalized non-symmetric eigenvalue problem (GNEP) on high performance computing (HPC) platforms with distributed memory. Such problems occur frequently in computational science and engineering, and our contributions make it possible to solve GNEPs fast and accurate in parallel using state-of-the-art HPC systems. A generalized eigenvalue problem corresponds to finding scalars y and vectors x such that Ax = yBx, where A and B are real square matrices. A nonzero x that satisfies the GNEP equation is called an eigenvector of the ordered pair (A,B), and the scalar y is the associated eigenvalue. Our contributions include parallel algorithms for transforming a matrix pair (A,B) to a generalized Schur form (S,T), where S is quasi upper triangular and T is upper triangular. The eigenvalues are revealed from the diagonals of S and T. Moreover, for a specified set of eigenvalues an associated pair of deflating subspaces can be computed, which typically is requested in various applications. In the first stage the matrix pair (A,B) is reduced to a Hessenberg-triangular form (H,T), where H is upper triangular with one nonzero subdiagonal and T is upper triangular, in a finite number of steps. The second stage reduces the matrix pair further to generalized Schur form (S,T) using an iterative QZ-based method. Outgoing from a one-stage method for the reduction from (A,B) to (H,T), a novel parallel algorithm is developed. In brief, a delayed update technique is applied to several partial steps, involving low level operations, before associated accumulated transformations are applied in a blocked fashion which together with a wave-front task scheduler makes the algorithm scale when running in a parallel setting. The potential presence of infinite eigenvalues makes a generalized eigenvalue problem ill-conditioned. Therefore the parallel algorithm for the second stage, reduction to (S,T) form, continuously scan for and robustly deflate infinite eigenvalues. This will reduce the impact so that they do not interfere with other real eigenvalues or are misinterpreted as real eigenvalues. In addition, our parallel iterative QZ-based algorithm makes use of multiple implicit shifts and an aggressive early deflation (AED) technique, which radically speeds up the convergence. The multi-shift strategy is based on independent chains of so called coupled bulges and computational windows which is an important source of making the algorithm scalable. The parallel algorithms have been implemented in state-of-the-art library software. The performance is demonstrated and evaluated using up to 1600 CPU cores for problems with matrices as large as 100000 x 100000. Our library software is described in a User Guide. The software is, optionally, tunable via a set of parameters for various thresholds and buffer sizes etc. These parameters are discussed, and recommended values are specified which should result in reasonable performance on HPC systems similar to the ones we have been running on.

  • 7.
    Adlerborn, Björn
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Kågström, Bo
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Karlsson, Lars
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Distributed one-stage Hessenberg-triangular reduction with wavefront scheduling2016Report (Other academic)
    Abstract [en]

    A novel parallel formulation of Hessenberg-triangular reduction of a regular matrix pair on distributed memory computers is presented. The formulation is based on a sequential cache-blocked algorithm by Kågstrom, Kressner, E.S. Quintana-Ortí, and G. Quintana-Ortí (2008). A static scheduling algorithm is proposed that addresses the problem of underutilized processes caused by two-sided updates of matrix pairs based on sequences of rotations. Experiments using up to 961 processes demonstrate that the new algorithm is an improvement of the state of the art but also identifies factors that currently limit its scalability.

  • 8.
    Adlerborn, Björn
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Kågström, Bo
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Kressner, Daniel
    A parallel QZ algorithm for distributed memory HPC systems2014In: SIAM Journal on Scientific Computing, ISSN 1064-8275, E-ISSN 1095-7197, Vol. 36, no 5, C480-C503 p.Article in journal (Refereed)
    Abstract [en]

    Appearing frequently in applications, generalized eigenvalue problems represent one of the core problems in numerical linear algebra. The QZ algorithm of Moler and Stewart is the most widely used algorithm for addressing such problems. Despite its importance, little attention has been paid to the parallelization of the QZ algorithm. The purpose of this work is to fill this gap. We propose a parallelization of the QZ algorithm that incorporates all modern ingredients of dense eigensolvers, such as multishift and aggressive early deflation techniques. To deal with (possibly many) infinite eigenvalues, a new parallel deflation strategy is developed. Numerical experiments for several random and application examples demonstrate the effectiveness of our algorithm on two different distributed memory HPC systems.

  • 9.
    Adlerborn, Björn
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Kågström, Bo
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Kressner, Daniel
    SB–MATHICSE–ANCHP, EPF Lausanne.
    PDHGEQZ user guide2015Report (Other academic)
    Abstract [en]

    Given a general matrix pair (A,B) with real entries, we provide software routines for computing a generalized Schur decomposition (S, T). The real and complex conjugate pairs of eigenvalues appear as 1×1 and 2×2 blocks, respectively, along the diagonals of (S, T) and can be reordered in any order. Typically, this functionality is used to compute orthogonal bases for a pair of deflating subspaces corresponding to a selected set of eigenvalues. The routines are written in Fortran 90 and targets distributed memory machines.

  • 10.
    Adlerborn, Björn
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Kågström, Bo
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Kressner, Daniel
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Parallel Variants of the Multishift QZ Algorithm with Advanced Deflation Techniques2007In: Applied Parallel Computing - State of the Art in Scientific Computing: 8th International Workshop, PARA 2006, Springer , 2007, 117-126 p.Conference paper (Refereed)
    Abstract [en]

    The QZ algorithm reduces a regular matrix pair to generalized Schur form, which can be used to address the generalized eigenvalue problem. This paper summarizes recent work on improving the performance of the QZ algorithm on serial machines and work in progress on a novel parallel implementation. In both cases, the QZ iterations are based on chasing chains of tiny bulges. This allows to formulate the majority of the computation in terms of matrix-matrix multiplications, resulting in natural parallelism and better performance on modern computing systems with memory hierarchies. In addition, advanced deflation strategies are used, specifically the so called aggressive early deflation, leading to a considerable convergence acceleration and consequently to a reduction of floating point operations and computing time.

  • 11.
    Afzaal, Qasim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ahmad, Usman
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Audio Video Streaming Solution for Bambuser2012Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Audio/Video streaming has widely been used in different applications but the social communication applications have especially raised its usage. The aim of this thesis is to design and develop an improved Audio/Video streaming solution for a Swedish company Bambuser and can easily be extended with new features where necessary. Currently Bambuser is using the Flash Media Server (FMS) for streaming the media, but it is license based and adds the extra cost to the company's budget. It does not support a wide range of platforms (e.g. OpenBSD and various Linux distributions) and also has limited options for the streaming. There is no real time monitoring and controlling functionality, which can show the status of essential services to the user, needed for the streaming (for example if the camera is working, microphone is turned on, battery power status. etc.).

    In order to solve these issues the GStreamer is used, which is an Open source multimedia streaming framework. The GStreamer environment was tested on different Linux distributions. The research and implementation includes the creation of the streaming pipeline and analyzing which options (i.e. GStreamer elements and plugins) are required to stream the media. It also includes the testing of different pipeline parameters (for example video rate, audio rate etc.) and noting their effects in a real working environment. Python binding with GStreamer is used to have better control over the pipeline. Another requirement of this project was to add the functionality of monitoring and control that shows the status of essential services to the user. Implementation of this part is done by using server and client side coding. Further improvements and suggestions are also proposed in this report.

  • 12.
    Ahlqvist, Emil
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Implementing a Resume Database with Online Learning to Rank2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Learning to Rank is a research area within Machine Learning. It is mainly used in Information Retrieval and has been applied to, among other systems, web search engines and in computational advertising. The purpose of the Learning to Rank model is to rank a list of items, placing the most relevant at the top of the list, according to the users' requirements. Online Learning to Rank is a type of this model, that learns directly from the users' interactions with the system.

    In this thesis a resume database is implemented, where the search engine applies an Online Learning to Rank algorithm, to rank consultant's resumes, when queries with required skills and competences are issued to the system. The implementation of the Resume Database and the ranking algorithm, as well as an evaluation, is presented in this report. Results from the evaluation indicates that the performance of the search engine, with the Online Learning to Rank algorithm, could be desirable in a production environment.

  • 13.
    Ahmad, Farooq
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Lindgren, Helena
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Selection of foundational ontology for collaborative knowledge modeling in healthcare domain2010In: Artificial intelligence: methodology, systems, and applications / [ed] Dicheva, Darina; Dochev, Danail, Springer Berlin/Heidelberg, 2010, 261-262 p.Conference paper (Refereed)
    Abstract [en]

    Ontology design is an important process for structuring knowledge to be reused in different projects in the health domain. In this paper, we describe an ontology design for the collaborative knowledge building system ACKTUS to be used for developing personalized knowledge applications for different domains. Different foundational ontologies were compared with respect to selected criteria considered vital for the project, such as modularity and descriptiveness.

  • 14. Aichroth, Patrick
    et al.
    Weigel, Christian
    Kurz, Thomas
    Stadler, Horst
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Björklund, Johanna
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Schlegel, Kai
    Berndl, Emanuel
    Perez, Antonio
    Bowyer, Alex
    Volpini, Andrea
    MICO - MEDIA IN CONTEXT2015In: 2015 IEEE International Conference on Multimedia & Expo Workshops (ICMEW), 2015Conference paper (Refereed)
    Abstract [en]

    The abundance of digital content requires cost-effective technologies to extract the hidden meaning from media objects. However, current approaches fail to deal with the challenges related to cross-media analysis, metadata publishing, querying and recommendation that are necessary to overcome this challenge. In this paper, we describe the EU project MICO (Media in Context) which aims to provide the necessary technologies based on open-source software (OSS) core components.

  • 15.
    Aimaiti, Nuerrennisahan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A Comparison of Rotation Parameterisations for Bundle Adjustment2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Bundle Adjustment is an iterative process where 3D information is estimated from 2D image measurements. Typically, the position of object points are estimated simultaneously with the position and orientation of the cameras. While the object points and camera positions have a straightforward "natural" parameterisation, several possibilities exist for the rotation. In this thesis, seven parameterisation of the rotation were investigated; Euler angles (two variants), the Rodriguez representation, the axis-and-angle representation, unit quaternions, and two variants of the direction cosine matrix (DCM). The Euler and Rodriguez parameterisation are common in photogrammetry and each has three parameters. The other parameterisations have more parameters and one or more constraint between them.

    The parameterisations were analyzed with respect to singularities, i.e. well-defined rotations that do not have any bounded and/or unique set of parameters. Four bundle adjustment experiments were setup, each corresponding to a singularity for one or more parameterisations. A fitth, singularity-free, experiment was also added. The experiments were perturbation studies that investigated the convergence properties of each parameterisation. The unconstrained parameterisations were solved by a damped and undamped Gauss-Newton algorithm, whereas the parameterisations with constraints were solved using damped and undamped algorithms based on the Gauss-Helmert estimation model.

    As expected, the parameterisations corresponding to the constructed singularity had higher failure rates and required more iterations and execution time than the others when it did converge. Excluding their singular cases, the Euler xyz and Rodriguez representations were the fastest with about 37% of the dcm. Of the singularity-free parameterisation, the unit quaternion was the fastest with 79% of the dcm.

    Surprisingly, the undamped bundle algorithms converged more often and faster than the damped bundle algorithms, even close to singularities. However, the undamped convergence was to a higher degree associated with numerical warnings and convergence toward angular values outside the nominal 2 range.

    The results suggest that if singularities are not expected, the Euler xyz and Rodriguez representations are the best of the tested parameterisations. Otherwise, the unit quaternion is the best. As an alternative to the latter case, the switching algorithm by Singla may be used, at the expense of a more complex algorithm.

  • 16.
    Aimaiti, Nuerrennisahan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Yan, Xu
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Gestire-based Interaction and Implication for the Future2011Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Currently there exists an advanced and natural form of interaction, named gesture-based interaction. It has been applied in some fields successfully, especially in the form of game applications. Although people are filled with wonder at the new interaction, it has not replaced the traditional interaction, like keyboard and mouse. From the user experience point of view, gesture-based interaction has advantages which traditional interactive form cannot offer, but also shortcomings which people seem dissatisfied with. This thesis focuses on expressing user experience of gesture-based interaction by conducting interview method. Finally, this paper presents a new design and tries to find implications for its practical usage in the future.

  • 17.
    Alaa, Alaqra
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    The Thing about gaming experience2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Despite the increasing popularity in the academic and practical fields of digital gaming, little has been explored and documented about gaming experience, especially firsthand account. This study uses Bruno Latour’s concept of the Thing while investigating digital gaming experience from frequent gamers’ standpoint using focus groups methodology. Additionally in-depth interviews were conducted with developers in order to gain a business perspective on the status of digital games development with regard to gamers. From the findings, Reality, Game, and Player were identified as agencies and their associations with the experiences of the gamers were gathered in making the Thing about gaming experience a matter of concern providing new meanings and further understandings of the abstract sets of experiences.

  • 18.
    Alaqra, Alaa
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Cell-phone Travel Planner GUI for SpaceTime2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Global positioning systems have been having an increasing interest recently and been integrated and used in many applications to service positioning, navigation and travel planning. This project has set to design and test an interface of a travel planner for cell phones. A pre-study was made to investigate other travel planners to help the design of this application that has targeted a user friendly interface that people can use regardless of their background. A special feature, carpooling, has been introduced to ease the environmental, economical, and social aspects of navigation. The test was done as walk-through mockup images case scenarios. The test subjects were pleased with the interface’s friendliness, invoked carpooling issues, presented contradictory opinions regarding the interface's design, and offered future integration with other applications suggestions all of which were discussed. Overall, the test results were positive and few problems with the overall design were identified. A future study with more participants and a deeper analysis of the interface would be one way to further investigate the proposed interface.

  • 19.
    Alexandersson, Calle
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    An evaluation of HTML5 components for web-based manipulation of tabular data2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    HTML5 is a promising technology that is on its way to becoming a standard for the web. Companies that have built their web application components using plugins now have to move to a entirely new JavaScript environment. One such component is data grids or tables and will be the focus of this report.

    In this report I present a proposal for evaluation criteria for tabular components in JavaScript frameworks. Using these criteria, grid components in some of the market leading frameworks are evaluated. Further I will for one of these frameworks present a test implementation and performance test focusing on load time with and without UI Virtualization.

  • 20.
    Ali, W
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Georgsson, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hellström, Thomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Visual tree detection for autonomous navigation in forest environment2008In: IEEE Intelligent Vehicles SymposiumConference Location: Eindhoven, NETHERLANDS, 2008, , 1144-1149 p.1144-1149 p.Conference paper (Refereed)
    Abstract [en]

    This paper describes a classification based tree detection method for autonomous navigation of forest vehicles in forest environment. Fusion of color, and texture cues has been used to segment the image into tree trunk and background objects. The segmentation of images into tree trunk and background objects is a challenging task due to high variations of illumination, effect of different color shades, non-homogeneous bark texture, shadows and foreshortening. To accomplish this, the approach has been to find the best combinations of color, and texture descriptors, and classification techniques. An additional task has been to estimate the distance between forest vehicle and the base of segmented trees using monocular vision. A simple heuristic distance measurement method is proposed that is based on pixel height and a reference width. The performance of various color and texture operators, and accuracy of classifiers has been evaluated using cross validation techniques.

  • 21.
    Ali-Eldin, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Capacity Scaling for Elastic Compute Clouds2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    AbstractCloud computing is a computing model that allows better management, higher utiliza-tion and reduced operating costs for datacenters while providing on demand resourceprovisioning for different customers. Data centers are often enormous in size andcomplexity. In order to fully realize the cloud computing model, efficient cloud man-agement software systems that can deal with the datacenter size and complexity needto be designed and built.This thesis studies automated cloud elasticity management, one of the main andcrucial datacenter management capabilities. Elasticity can be defined as the abilityof cloud infrastructures to rapidly change the amount of resources allocated to anapplication in the cloud according to its demand. This work introduces algorithms,techniques and tools that a cloud provider can use to automate dynamic resource pro-visioning allowing the provider to better manage the datacenter resources. We designtwo automated elasticity algorithms for cloud infrastructures that predict the futureload for an application running on the cloud. It is assumed that a request is either ser-viced or dropped after one time unit, that all requests are homogeneous and that it takesone time unit to add or remove resources. We discuss the different design approachesfor elasticity controllers and evaluate our algorithms using real workload traces. Wecompare the performance of our algorithms with a state-of-the-art controller. We ex-tend on the design of the best performing controller out of our two controllers anddrop the assumptions made during the first design. The controller is evaluated with aset of different real workloads.All controllers are designed using certain assumptions on the underlying systemmodel and operating conditions. This limits a controller’s performance if the modelor operating conditions change. With this as a starting point, we design a workloadanalysis and classification tool that assigns a workload to its most suitable elasticitycontroller out of a set of implemented controllers. The tool has two main components,an analyzer and a classifier. The analyzer analyzes a workload and feeds the analysisresults to the classifier. The classifier assigns a workload to the most suitable elasticitycontroller based on the workload characteristics and a set of predefined business levelobjectives. The tool is evaluated with a set of collected real workloads and a set ofgenerated synthetic workloads. Our evaluation results shows that the tool can help acloud provider to improve the QoS provided to the customers.

  • 22.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    El-Ansary, Sameh
    Nile University.
    Replica Placement in Peer-Assisted Clouds: An Economic Approach2011In: Lecture Notes in Computer Science / [ed] Pascal Felber, Romain Rouvoy, Springer, 2011, 208-213 p.Conference paper (Refereed)
    Abstract [en]

    We introduce NileStore, a replica placement algorithm based on an economical model for use in Peer-assisted cloud storage. The algorithm uses storage and bandwidth resources of peers to offload the cloud provider’s resources. We formulate the placement problem as a linear task assignment problem where the aim is to minimize time needed for file replicas to reach a certain desired threshold. Using simulation, We reduce the probability of a file being served from the provider’s servers by more than 97.5% under realistic network conditions.

  • 23.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    El-Ansary, Sameh
    Nile University.
    Optimizing Replica Placement in Peer-Assisted Cloud Stores2011Conference paper (Refereed)
    Abstract [en]

    Peer-assisted cloud storage systems use the unutilizedresources of the clients subscribed to a storage cloudto offload the servers of the cloud. The provider distributesdata replicas on the clients instead of replicating on the localinfrastructure. These replicas allow the provider to providea highly available, reliable and cheap service at a reducedcost. In this work we introduce NileStore, a protocol forreplication management in peer-assisted cloud storage. Theprotocol converts the replica placement problem into a lineartask assignment problem. We design five utility functionsto optimize placement taking into account the bandwidth,free storage and the size of data in need of replication oneach peer. The problem is solved using a suboptimal greedyoptimization algorithm. We show our simulation results usingthe different utilities under realistic network conditions. Ourresults show that using our approach offloads the cloud serversby about 90% compared to a random placement algorithmwhile consuming 98.5% less resources compared to a normalstorage cloud.

  • 24.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ilyushkin, Alexey
    Ghit, Bogdan
    Herbst, Nikolas Roman
    Papadopoulos, Alessandro
    Losup, Alexandru
    Which Cloud Auto-Scaler Should I Use for my Application?: Benchmarking Auto-Scaling Algorithms2016In: PROCEEDINGS OF THE 2016 ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE'16), Association for Computing Machinery (ACM), 2016, 131-132 p.Conference paper (Refereed)
  • 25.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Lund University.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Analysis and characterization of a Video-on-Demand service workload2015In: Proceedings of the 6th ACM Multimedia Systems Conference, MMSys 2015, ACM Digital Library, 2015, 189-200 p.Conference paper (Refereed)
    Abstract [en]

    Video-on-Demand (VoD) and video sharing services accountfor a large percentage of the total downstream Internet traf-fic. In order to provide a better understanding of the loadon these services, we analyze and model a workload tracefrom a VoD service provided by a major Swedish TV broad-caster. The trace contains over half a million requests gener-ated by more than 20000 unique users. Among other things,we study the request arrival rate, the inter-arrival time, thespikes in the workload, the video popularity distribution, thestreaming bit-rate distribution and the video duration distri-bution. Our results show that the user and the session ar-rival rates for the TV4 workload does not follow a Poissonprocess. The arrival rate distribution is modeled using a log-normal distribution while the inter-arrival time distributionis modeled using a stretched exponential distribution. Weobserve the “impatient user” behavior where users abandonstreaming sessions after minutes or even seconds of startingthem. Both very popular videos and non-popular videos areparticularly affected by impatient users. We investigate ifthis behavior is an invariant for VoD workloads.

  • 26.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Dept. of Electrical and Information Technology, Lund University, Lund, Sweden.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Efficient provisioning of bursty scientific workloads on the cloud using adaptive elasticity control2012In: Proceedings of the 3rd workshop on Scientific Cloud Computing Date, Association for Computing Machinery (ACM), 2012, 31-40 p.Conference paper (Refereed)
    Abstract [en]

    Elasticity is the ability of a cloud infrastructure to dynamically change theamount of resources allocated to a running service as load changes. We build anautonomous elasticity controller that changes the number of virtual machinesallocated to a service based on both monitored load changes and predictions offuture load. The cloud infrastructure is modeled as a G/G/N queue. This modelis used to construct a hybrid reactive-adaptive controller that quickly reactsto sudden load changes, prevents premature release of resources, takes intoaccount the heterogeneity of the workload, and avoids oscillations. Using simulations with Web and cluster workload traces, we show that our proposed controller lowers the number of delayed requests by a factor of 70 for the Web traces and 3 for the cluster traces when compared to a reactive controller. Ourcontroller also decreases the average number of queued requests by a factor of 3 for both traces, and reduces oscillations by a factor of 7 for the Web traces and 3 for the cluster traces. This comes at the expense of between 20% and 30% over-provisioning, as compared to a few percent for the reactive controller.

  • 27.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Rezaie, Ali
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Mehta, Amardeep
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Razroev, Stanislav
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Sjöstedt-de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Seleznjev, Oleg
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    How will your workload look like in 6 years?: Analyzing Wikimedia's workload2014In: Proceedings of the 2014 IEEE International Conference on Cloud Engineering (IC2E 2014) / [ed] Lisa O’Conner, IEEE Computer Society, 2014, 349-354 p.Conference paper (Refereed)
    Abstract [en]

    Accurate understanding of workloads is key to efficient cloud resource management as well as to the design of large-scale applications. We analyze and model the workload of Wikipedia, one of the world's largest web sites. With descriptive statistics, time-series analysis, and polynomial splines, we study the trend and seasonality of the workload, its evolution over the years, and also investigate patterns in page popularity. Our results indicate that the workload is highly predictable with a strong seasonality. Our short term prediction algorithm is able to predict the workload with a Mean Absolute Percentage Error of around 2%.

  • 28.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Seleznjev, Oleg
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Sjöstedt-de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Measuring cloud workload burstiness2014In: 2014 IEEE/ACM 7th International Conference on Utility and Cloud Computing (UCC), IEEE conference proceedings, 2014, 566-572 p.Conference paper (Refereed)
    Abstract [en]

    Workload burstiness and spikes are among the main reasons for service disruptions and decrease in the Quality-of-Service (QoS) of online services. They are hurdles that complicate autonomic resource management of datacenters. In this paper, we review the state-of-the-art in online identification of workload spikes and quantifying burstiness. The applicability of some of the proposed techniques is examined for Cloud systems where various workloads are co-hosted on the same platform. We discuss Sample Entropy (SampEn), a measure used in biomedical signal analysis, as a potential measure for burstiness. A modification to the original measure is introduced to make it more suitable for Cloud workloads.

  • 29.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    An adaptive hybrid elasticity controller for cloud infrastructures2012In: 2012 IEEE Network operations and managent symposium (NOMS), IEEE Communications Society, 2012, 204-212 p.Conference paper (Refereed)
    Abstract [en]

    Cloud elasticity is the ability of the cloud infrastructure to rapidly change the amount of resources allocated to a service in order to meet the actual varying demands on the service while enforcing SLAs. In this paper, we focus on horizontal elasticity, the ability of the infrastructure to add or remove virtual machines allocated to a service deployed in the cloud. We model a cloud service using queuing theory. Using that model we build two adaptive proactive controllers that estimate the future load on a service. We explore the different possible scenarios for deploying a proactive elasticity controller coupled with a reactive elasticity controller in the cloud. Using simulation with workload traces from the FIFA world-cup web servers, we show that a hybrid controller that incorporates a reactive controller for scale up coupled with our proactive controllers for scale down decisions reduces SLA violations by a factor of 2 to 10 compared to a regression based controller or a completely reactive controller.

  • 30.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Department of Electrical and Information Technology, Lund University, Lund, Sweden.
    Workload Classification for Efficient Auto-Scaling of Cloud Resources2013Manuscript (preprint) (Other academic)
    Abstract [en]

    Elasticity algorithms for cloud infrastructures dynamically change the amount of resources allocated to a running service according to the current and predicted future load. Since there is no perfect predictor, and since different applications’ workloads have different characteristics, no single elasticity algorithm is suitable for future predictions for all workloads. In this work, we introduceWAC, aWorkload Analysis and Classification tool that analyzes workloads and assigns them to the most suitable elasticity controllers based on the workloads’ characteristics and a set of business level objectives.

    WAC has two main components, the analyzer and the classifier. The analyzer analyzes workloads to extract some of the features used by the classifier, namely, workloads’ autocorrelations and sample entropies which measure the periodicity and the burstiness of the workloads respectively. These two features are used with the business level objectives by the clas-sifier as the features used to assign workloads to elasticity controllers. We start by analyzing 14 real workloads available from different applications. In addition, a set of 55 workloads is generated to test WAC on more workload configurations. We implement four state of the art elasticity algorithms. The controllers are the classes to which the classifier assigns workloads. We use a K nearest neighbors classifier and experiment with different workload combinations as training and test sets. Our experi-ments show that, when the classifier is tuned carefully, WAC correctly classifies between 92% and 98.3% of the workloads to the most suitable elasticity controller.

  • 31.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Lund University.
    WAC: A Workload analysis and classification tool for automatic selection of cloud auto-scaling methodsManuscript (preprint) (Other academic)
    Abstract [en]

    Autoscaling algorithms for elastic cloud infrastructures dynami-cally change the amount of resources allocated to a service ac-cording to the current and predicted future load. Since there areno perfect predictors, no single elasticity algorithm is suitable foraccurate predictions of all workloads. To improve the quality ofworkload predictions and increase the Quality-of-Service (QoS)guarantees of a cloud service, multiple autoscalers suitable for dif-ferent workload classes need to be used. In this work, we intro-duce WAC, a Workload Analysis and Classification tool that as-signs workloads to the most suitable elasticity autoscaler out of aset of pre-deployed autoscalers. The workload assignment is basedon the workload characteristics and a set of user-defined Business-Level-Objectives (BLO). We describe the tool design and its maincomponents. We implement WAC and evaluate its precision us-ing various workloads, BLO combinations and state-of-the-art au-toscalers. Our experiments show that, when the classifier is tunedcarefully, WAC assigns between 87% and 98.3% of the workloadsto the most suitable elasticity autoscaler.

  • 32.
    Ali-Eldin Hassan, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Workload characterization, controller design and performance evaluation for cloud capacity autoscaling2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis studies cloud capacity auto-scaling, or how to provision and release re-sources to a service running in the cloud based on its actual demand using an auto-matic controller. As the performance of server systems depends on the system design,the system implementation, and the workloads the system is subjected to, we focuson these aspects with respect to designing auto-scaling algorithms. Towards this goal,we design and implement two auto-scaling algorithms for cloud infrastructures. Thealgorithms predict the future load for an application running in the cloud. We discussthe different approaches to designing an auto-scaler combining reactive and proactivecontrol methods, and to be able to handle long running requests, e.g., tasks runningfor longer than the actuation interval, in a cloud. We compare the performance ofour algorithms with state-of-the-art auto-scalers and evaluate the controllers’ perfor-mance with a set of workloads. As any controller is designed with an assumptionon the operating conditions and system dynamics, the performance of an auto-scalervaries with different workloads.In order to better understand the workload dynamics and evolution, we analyze a6-years long workload trace of the sixth most popular Internet website. In addition,we analyze a workload from one of the largest Video-on-Demand streaming servicesin Sweden. We discuss the popularity of objects served by the two services, the spikesin the two workloads, and the invariants in the workloads. We also introduce, a mea-sure for the disorder in a workload, i.e., the amount of burstiness. The measure isbased on Sample Entropy, an empirical statistic used in biomedical signal processingto characterize biomedical signals. The introduced measure can be used to charac-terize the workloads based on their burstiness profiles. We compare our introducedmeasure with the literature on quantifying burstiness in a server workload, and showthe advantages of our introduced measure.To better understand the tradeoffs between using different auto-scalers with differ-ent workloads, we design a framework to compare auto-scalers and give probabilisticguarantees on the performance in worst-case scenarios. Using different evaluation cri-teria and more than 700 workload traces, we compare six state-of-the-art auto-scalersthat we believe represent the development of the field in the past 8 years. Knowingthat the auto-scalers’ performance depends on the workloads, we design a workloadanalysis and classification tool that assigns a workload to its most suitable elasticitycontroller out of a set of implemented controllers. The tool has two main components;an analyzer, and a classifier. The analyzer analyzes a workload and feeds the analysisresults to the classifier. The classifier assigns a workload to the most suitable elasticitycontroller based on the workload characteristics and a set of predefined business levelobjectives. The tool is evaluated with a set of collected real workloads, and a set ofgenerated synthetic workloads. Our evaluation results shows that the tool can help acloud provider to improve the QoS provided to the customers.

  • 33.
    Alin, Lars
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Object Tracking withIphone 3Gs2010Independent thesis Advanced level (degree of Master (One Year)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    In June of 2007 Apple Inc. released the smartphone Iphone. It was a groundbreaking success that set a new standard for what a smartphone should be able to do. Apple has improved the Iphone every year since then and the 3Gs is the newest Iphone model. As the phones have improved, both when looking at hardware and software, the applications have improved as well. The Iphone 3Gs provides the possibility to use the camera as an application background and with that the possibility to analyze the surroundings, making it possible to track objects that the phone is pointed towards.This thesis examines how object tracking can be implemented in applications for Iphone 3Gs as well as providing a survey of four different areas of use that have been implemented in Xcode: an augmented reality car game, a letter tracking application, a face recognition application and an object recognition application.

  • 34.
    Andersson, Christer
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    En jämförelsestudie av JavaScript-bibliotek Med fokus på mjukvarukvalitet2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    JavaScripts popularity is increasing and the number of libraries too. This report focuses on well-known software metrics in complexity, maintainability and different size-metrics. A few different JavaScript libraries are compared and analyzed. The result shows that there are indeed differences, mostly in size- and complexity-measures where some functions are implemented with a higher complexity.

  • 35.
    Andersson, Håkan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    School Timetabling in Theory and Practice A comparative study of Simulated Annealing and Tabu Search2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    School timetabling is way of distributing resources such as teachers and classrooms over a fixed period of time. This task can be difficult and very time-consuming. If the process of generating timetables is automated with the help of algorithms then this can help save both time and money for the educational institute.

    In this thesis a general timetable is presented along with a set of constraints commonly used in school timetabling. Two meta heuristic algorithms with previous satisfying results, Simulated Annealing and Tabu Search, are implemented and benchmarked against each other in order to evaluate the performance of these.

    The results show that although both algorithms are good candidates for creating timetables, Simulated Annealing has the edge both in run time and the quality of the timetable.

  • 36.
    Andersson, Ludwig
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Natural Language Processing In A Distributed  Environment: A comparative performance analysis of Apache Spark and Hadoop MapReduce2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A big majority of the data hosted on the internet today is in natural text and therefore understanding natural language and how to effectively process and analyzing text has become a big part of data mining. Natural Language Processing has many applications in fields such as business intelligence and security purposes.The problem with natural language text processing and analyzing is the computational power needed to perform the actual processing, performance of personal computer has not kept up with amounts of data that needs to be processed so another approach with good performance scaling potential is needed.This study does a preliminary comparative performance analysis of processing natural language text in an distributed environment using two popular open-source frameworks, Hadoop MapReduce and Apache Spark.

  • 37.
    Andersson, Ola
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Threat, risk, and vulnerabilityanalyses during the developmentof IT systems in the SwedishArmed Forces2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master’s thesis describes how two models from the Swedish Armed Forces; the risk management model and the IT lifecycle model can be combined. An example is then presented for how the risk management model can be extended for threats, risks, and vulnerabilities related to information technology. The combination and extension of the models are based on a literature study that lists and compares models and methods for threat, risk, andvulnerability analyses, as well as an analysis of threats related to information technology. From the combined and extended model, a design proposal for how to implement the identified functionality was identified. Based on an evaluation that showed that the program NTE and the plugin EASTER were suitable as the foundation for this implementation, the program NTE and the plugin EASTER were extended with further functionality and resulted in the implementation of the plugin ASCENSION. This was evaluated and resulted in ideas for a possible re-design and examples of the future potential of ASCENSION.

  • 38.
    Andersson, Per
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Granat, Robert
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, HPC2N (High Performance Computing Centre North).
    Jonsson, Isak
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, HPC2N (High Performance Computing Centre North).
    Kågström, Bo
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, HPC2N (High Performance Computing Centre North).
    Parallel Algorithms for Triangular Periodic Sylvester-Type Matrix Equations2008In: Euro-Par 2008 - Parallel Processing: 14th International Euro-Par Conference Conference Location: Las Palmas de Gran Canaria, SPAIN, Springer , 2008, 780-789 p.Conference paper (Refereed)
    Abstract [en]

    We present parallel algorithms for triangular periodic Sylvester-type matrix equations, conceptually being the third step of a periodic Bartels-Stewart-like solution method for general periodic Sylvester-type matrix equations based on variants of the periodic Schur decomposition. The presented algorithms are designed and implemented in the framework of the recently developed HPG library SCASY and are based on explicit blocking, 2-dimensional block cyclic data distribution and a wavefront-like traversal of the right hand side matrices. High performance is obtained by rich usage of level 3 BLAS operations. It is also demonstrated how several important key concepts of SCASY regarding communications and the treatment of quasi-triangular coefficient matrices are generalized to the periodic case. Some experimental results from a distributed memory Linux cluster demonstrate are also presented.

  • 39.
    Andersson, Peter
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Model based object finding in occluded cluttered environments2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of the thesis is object finding in occluded and cluttered environment using computer vision techniques and robot motion. Difficulties of the object finding are 1. finding objects at hidden area and 2. finding unrecognized objects. For solving the difficulties, two methods were developed, one is for finding objects in occluded cluttered environments using model based object finding and the other to increase the robustness in object finding by identifying known objects that are unidentified. The goal was to search occluded areas with the bumblebee2 stereo camera to be able to identify all known objects in the environment by removing all visible known objects To identify known objects SURF [9] was used and to be able to remove the identified objects their location first needed to be localized. To localize the object‘s x and y coordinate the information from SURF [9] was used, and the distance coordinate z is calculated using the depth image from the stereo camera. The method to identify objects the SURF [9] algorithm had missed to identify uses a method to find unknown segments in the environment. By using a push motion on the segments to change their angle it can remove possible light reflections and the object can be identified. The results of this research show that the method can find objects in occluded cluttered areas and it can also identified missed known objects.

  • 40.
    Andersson, Rickard
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Pseudo-optimal strategies in no-limit poker2006In: ICGA Journal, ISSN 1389-6911, Vol. 29, no 3, 143-149 p.Article in journal (Refereed)
    Abstract [en]

    Games have always been a strong driving force in Artificial Intelligence. In the last ten years huge improvements has been made in perfect information games like chess and Othello. The strongest computer agents can nowadays beat the strongest human players. This is not the case for imperfect information games such as poker and bridge where creating an expert computer player has shown to be much harder. Previous research in poker has either addressed limit poker or simplified variations of poker games. This paper tries to extend known techniques successfully used in limit poker to no-limit. No-limit poker increases the size of the game tree drastically. To reduce the complexity an abstracted model of the game is created. Finding an optimal strategy for the new model is now a minimization problem using linear programming techniques. The result is a set of pseudo-optimal strategies for no-limit Texas Hold'em. A bot named AGGROBOT was built from these strategies which perform well as long as the players' stack sizes are fairly small.

  • 41.
    Andersson Thunberg, Karl
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Large Scale Server Publishing for Dynamic Content2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The number of interactive and dynamic web services on the Internet is growing more and more and to accommodate as much functionality as possible, many techniques for asynchronous web communication are being developed. This thesis report describes the evaluation of an existing web service that uses bidirectional communication over the web to provide voting functionality in real-time on web pages. The thesis consists of an assessment of problem domains, an evaluation of the system and an implementation of some of the identified problems. It focuses on a few core issues of the current solution, namely the communication techniques between the client and the server, the setup of the overarching structure of the system and the separation of messaging channels for different use cases.The evaluation of the reference system was motivated by addressing the issue of being able to packet the service better as a product and create a distinction between the use case and the underlying system. It was done so that the stakeholders of the product may more easily define the way the service can be used and so that a better course of action can be taken for continuing the development of the service. The implemented solution shows an example of how the messaging channels could be separated and what kind of trade-os exist between the current and implemented solution.

  • 42.
    André, Caroline
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Design aspects in a mobile biofeedback system - developmentof a new interface concept usingdesign qualities2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It has been established that long term stress can lead to chronic illness of cardiac disease and vascular disorder. In the way people live their lives today they are surrounded by stress and they contribute to the stressful society when they constantly chase the time. The Mobile Life Centre explores how the system Aective Health can get people to reect up on their stress levels and connect that to their everyday activities by using bio sensors and a mobile phone. The bio sensor data visualization in the interface of the system is today tied to time. Since time is perceived dierently from person to person that is something that has caused problems for the design team of Aective Health. This thesis examines how dierent representations of time in user interfaces can be used to mediate the design qualities of subjective time, aliveness and uency in the Aective Health system. As a result from investigating the time aspect and how time can be visualized in a subjective way a suggestion for a design solution was developed.

  • 43.
    Anjum, Chaudhary
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Learner’s Interaction With Information and Communication Technologies2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This Master’s thesis aims to explore how children and teen-agers (i.e. learners) interact and create a use for information and communication technology in the classroom during their lectures. The study is based on distributed cognition theory in order to describe a cognitive  system which involves interactions among humans (i.e. learners), artifacts which they use (i.e. information and communication technology active boards) and the environment in which they interact (i.e. a classroom).

    User’s (such as the children, teen-agers and teachers) interaction with information and communication technology can lead towards new and important ways of invention in the classroom. No doubt the ideas, thoughts and vision of these users (such as children and teenagers) are very important which can change an environment that supports learning. The Distributed Cognition Approach is a widely acknowledged approach, but it is less commonly applied in order to observe learner’s (such as children and teen-agers) interaction with information and communication technologies in their learning setting. Therefore this study aims to explore the children and teen-agers interaction with the information and communication technology active boards by using distributed cognition theory which can be expressed as important and interesting for the researchers, designers and developers in evaluating, designing and developing effective interactive technologies that supports better education.

    Through an empirical case study, qualitative data have been collected using interviews and observations. Based on related research, related theory, qualitative results and analysis, a conclusion is presented which shows that (with the help of the analysis of distributed cognition theory) the information and communication technology active boards seems to engage the children and teen-ager’s to collaborative learning activities which supports collaboration and shared knowledge. It helps to capture their concentration towards learning which can increase the opportunities and possibilities of better learning results related to their education.

    The distributed cognition approach provides an analytic and investigative methodology in order to examine the learner’s interactions with artifacts which are difficult with other traditional methodologies to the analysis of cognitive-tasks. This approach highlights the complicated interdependencies among learners and artifacts in collaborative learning activities.

  • 44.
    Anttila, L.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Eklund, Patrik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kallin, Lena
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Koskinen, P.
    Penttilä, T.-A.
    The Generalised Preprocessing Perceptron for Medical Data Analysis: A Case Study for the Polycystic Ovary Syndrome1996In: Cybernetics and Systems '96: Proceedings of the 13th European Meeting on Cybernetics and Systems Research / [ed] Robert Trappl, 1996, 597-602 p.Conference paper (Other academic)
  • 45. Arafat, Yeasin
    et al.
    Hellström, Thomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Rashid, Jayedur
    Parameterized sensor model and an approach for measuring goodness of robotic maps2010In: Proceedings of the 15th IASTED International Conference on Robotics and Applications (RA 2010), 2010Conference paper (Refereed)
  • 46.
    Armgren, Marc
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Mobile Cross-platform development versus native development A look at Xamarin Platform2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The world of mobile phones is currently inhabited by three large rivals. We have Apple with their iOS devices, Microsoft with the Windows Phone line, and various devices with Googles Android operating system. Developing for all platforms individually is labour intensive and time consuming. Therefore cross-platform development is of interest for companies large as small. The technique which gives performance closest to native development is called cross compiling, which compiles native applications from a common codebase. This thesis takes a closer look at the performance of the tool Xamarin Platform, in which applications for iOS, Windows Phone and Android can be created. The performance of Xamarin Platform applications on iOS and Android is native for most user interface components. Network performance is native or better. However computational tasks are very slow compared to natively developed applications. Xamarin PlatformWindows Phone applications are not covered by this thesis.

  • 47.
    Armstrong, Django
    et al.
    School of Computing, University of Leeds.
    Djemame, Karin
    School of Computing, University of Leeds.
    Nair, Srijith
    British Telecom.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ziegler, Wolfgang
    Fraunhofer SCAI.
    Towards a Contextualization Solution for Cloud Platform Services2011In: 2011 IEEE Third International Conference on Cloud Computing Technology and Science, IEEE Computer Society, 2011, 328-331 p.Conference paper (Refereed)
    Abstract [en]

    We propose a cloud contextualization mechanism which operates in two stages, contextualization of VM images prior to service deployment (PaaS level) and self-contextualization of VM instances created from the image (IaaS level). The contextualization tools are implemented as part of the OPTIMIS Toolkit, a set of software components for simplified management of cloud services and infrastructures. We present the architecture of our contextualization tools and the feasibility of our contextualization mechanism is demonstrated in a three-tier web application scenario. Preliminary performance results suggest acceptable performance and scalability.

  • 48.
    Armstrong, Django
    et al.
    University of Leeds.
    Espling, Daniel
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Djemame, Karim
    University of Leeds.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Contextualization: dynamic configuration of virtual machines2015In: Journal of Cloud Computing - Advances, Systems and Applications, ISSN 2192-113X, Vol. 4, no 17, 1-15 p.Article in journal (Refereed)
    Abstract [en]

    New VM instances are created from static templates that contain the basic configuration of the VM to achieve elasticity with regards to capacity. Instance specific settings can be injected into the VM during the deployment phase through means of contextualization. So far this is limited to a single data source and data remains static throughout the lifecycle of the VM.

    We present a layered approach to contextualization that supports different classes of contextualization data available from several sources. The settings are made available to the VM through virtual devices. Inside each VM data from different classes are layered on top of each other to create a unified file hierarchy.

    Context data can be modified during runtime by updating the contents of the virtual devices, making our approach the first contextualization approach to natively support recontextualization. Recontextualization enables runtime reconfiguration of an executing service and can act as a trigger and key enabler of self-* techniques. This trigger provides a service with a mechanism to adapt or optimize itself in response to a changing environment. The runtime reconfiguration using recontextualization and its potential gains are illustrated in an example with a distributed file system, demonstrating the feasibility of our approach.

  • 49.
    Armstrong, Django
    et al.
    University of Leeds.
    Espling, Daniel
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Djemame, Karim
    University of Leeds.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Runtime Virtual Machine Recontextualization for Clouds2013In: Euro-Par 2012: Parallel Processing Workshops: Euro-Par 2012: Parallel Processing Workshops , volume 7640 / [ed] Caragiannis et al., Springer Berlin/Heidelberg, 2013, 567-576 p.Conference paper (Refereed)
    Abstract [en]

    We introduce and define the concept of recontextualization for cloud applications by extending contextualization, i.e. the dynamic configuration of virtual machines (VM) upon initialization, with autonomous updates during runtime. Recontextualization allows VM images and instances to be dynamically re-configured without restarts or downtime, and the concept is applicable to all aspects of configuring a VM from virtual hardware to multi-tier software stacks. Moreover, we propose a runtime cloud recontextualization mechanism based on virtual device management that enables recontextualization without the need to customize the guest VM. We illustrate our concept and validate our mechanism via a use case demonstration: the reconfiguration of a cross-cloud migratable monitoring service in a dynamic cloud environment. We discuss the details of the interoperable recontextualization mechanism, its architecture and demonstrate a proof of concept implementation. A performance evaluation illustrates the feasibility of the approach and shows that the recontextualization mechanism performs adequately with an overhead of 18% of the total migration time.

  • 50. Asan, Noor Badariah
    et al.
    Noreland, Daniel
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Hassan, Emadeldeen
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Department of Electronics and Electrical Communications, Menoufia University, Menouf, Egypt.
    Shah, Syaiful Redzwan Mohd
    Rydberg, Anders
    Blokhuis, Taco J.
    Carlsson, Per-Ola
    Voigt, Thiemo
    Augustine, Robin
    Intra-body microwave communication through adipose tissue2017In: Healthcare technology letters, E-ISSN 2053-3713, Vol. 4, no 4, 115-121 p.Article in journal (Refereed)
    Abstract [en]

    The human body can act as a medium for the transmission of electromagnetic waves in the wireless body sensor networks context. However, there are transmission losses in biological tissues due to the presence of water and salts. This Letter focuses on lateral intra-body microwave communication through different biological tissue layers and demonstrates the effect of the tissue thicknesses by comparing signal coupling in the channel. For this work, the authors utilise the R-band frequencies since it overlaps the industrial, scientific and medical radio (ISM) band. The channel model in human tissues is proposed based on electromagnetic simulations, validated using equivalent phantom and ex-vivo measurements. The phantom and ex-vivo measurements are compared with simulation modelling. The results show that electromagnetic communication is feasible in the adipose tissue layer with a low attenuation of approximate to 2 dB per 20 mm for phantom measurements and 4 dB per 20 mm for ex-vivo measurements at 2 GHz. Since the dielectric losses of human adipose tissues are almost half of ex-vivo tissue, an attenuation of around 3 dB per 20 mm is expected. The results show that human adipose tissue can be used as an intra-body communication channel.

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