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  • 1.
    Bohlin, Ludvig
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edler, Daniel
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lancichinetti, Andrea
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rosval, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Community Detection and Visualization of Networks with the Map Equation Framework2014In: Measuring Scholarly Impact: Methods and Practice / [ed] Ying Ding, Ronald Rousseau, Dietmar Wolfram, Springer, 2014, p. 3-34Chapter in book (Refereed)
    Abstract [en]

    Large networks contain plentiful information about the organization of a system. The challenge is to extract useful information buried in the structure of myriad nodes and links. Therefore, powerful tools for simplifying and highlighting important structures in networks are essential for comprehending their organization. Such tools are called community-detection methods and they are designed to identify strongly intraconnected modules that often correspond to important functional units. Here we describe one such method, known as the map equation, and its accompanying algorithms for finding, evaluating, and visualizing the modular organization of networks. The map equation framework is very flexible and can identify two-level, multi-level, and overlapping organization in weighted, directed, and multiplex networks with its search algorithm Infomap. Because the map equation framework operates on the flow induced by the links of a network, it naturally captures flow of ideas and citation flow, and is therefore well-suited for analysis of bibliometric networks.

  • 2.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Sjölander, Mattias
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Eriksson, Erik J.
    ICT Services and System Development (ITS), Umeå University, Umeå, Sweden.
    Strategic Environmental Archaeology Database (SEAD)2018In: Encyclopedia of global archaeology / [ed] Smith, C., Cham: Springer, 2018, 2Chapter in book (Refereed)
    Abstract [en]

    Environmental archaeology encompasses a wide range of scientific methods for analyzing the results of past human activities, environments, climates, and perhaps, most importantly, the relationships between these. Many of these methods are referred to as proxy analyses, denoting the illumination of the past as interpreted indirectly through the evidence of fossil organisms or properties. These lines of evidence, or proxy data sources, are assumed to reflect past conditions by way of their dependence on them. For example, a species of beetle may only survive within a specific climate range, and thus its presence in samples indicates this climate at the time of deposition; organic waste deposited around a farmstead will raise soil phosphate levels above those of the surrounding land; and the presence of cereal grains in postholes suggests their local cultivation or import, usage, or storage.

  • 3.
    Calatayud, Joaquín
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bernardo-Madrid, Ruben
    Neuman, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rojas, Alexis
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rosvall, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Exploring the solution landscape enables more reliable network community detection2019In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 100, no 5, article id 052308Article in journal (Refereed)
    Abstract [en]

    To understand how a complex system is organized and functions, researchers often identify communities in the system's network of interactions. Because it is practically impossible to explore all solutions to guarantee the best one, many community-detection algorithms rely on multiple stochastic searches. But for a given combination of network and stochastic algorithms, how many searches are sufficient to find a solution that is good enough? The standard approach is to pick a reasonably large number of searches and select the network partition with the highest quality or derive a consensus solution based on all network partitions. However, if different partitions have similar qualities such that the solution landscape is degenerate, the single best partition may miss relevant information, and a consensus solution may blur complementary communities. Here we address this degeneracy problem with coarse-grained descriptions of the solution landscape. We cluster network partitions based on their similarity and suggest an approach to determine the minimum number of searches required to describe the solution landscape adequately. To make good use of all partitions, we also propose different ways to explore the solution landscape, including a significance clustering procedure. We test these approaches on synthetic networks and a real-world network using two contrasting community-detection algorithms: The algorithm that can identify more general structures requires more searches, and networks with clearer community structures require fewer searches. We also find that exploring the coarse-grained solution landscape can reveal complementary solutions and enable more reliable community detection.

  • 4. Durango, Jonas
    et al.
    Dellkrantz, Manfred
    Maggio, Martina
    Klein, Cristian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Papadopoulos, Alessandro Vittorio
    Hernandez-Rodriguez, Francisco
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Arzen, Karl-Erik
    Control-theoretical load-balancing for cloud applications with brownout2014In: 2014 IEEE 53RD ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), 2014, p. 5320-5327Conference paper (Refereed)
    Abstract [en]

    Cloud applications are often subject to unexpected events like flash crowds and hardware failures. Without a predictable behaviour, users may abandon an unresponsive application. This problem has been partially solved on two separate fronts: first, by adding a self-adaptive feature called brownout inside cloud applications to bound response times by modulating user experience, and, second, by introducing replicas - copies of the applications having the same functionalities - for redundancy and adding a load-balancer to direct incoming traffic. However, existing load-balancing strategies interfere with brownout self-adaptivity. Load-balancers are often based on response times, that are already controlled by the self-adaptive features of the application, hence they are not a good indicator of how well a replica is performing. In this paper, we present novel load-balancing strategies, specifically designed to support brownout applications. They base their decision not on response time, but on user experience degradation. We implemented our strategies in a self-adaptive application simulator, together with some state-of-the-art solutions. Results obtained in multiple scenarios show that the proposed strategies bring significant improvements when compared to the state-of-the-art ones.

  • 5.
    Eklund, Pauline
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Implementering av ISOBUS på ECU vid Ålö AB2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A serial bus called ISOBUS based on CAN is becoming more and more common in the agriculture and forestry industry. The bus specifies communication between tractors and their implements. Earlier each implement had its own monitor to show its functionalities, which could lead to a lot of monitors in the tractor cabin. ISOBUS requires only one monitor, called VT (Virtual Terminal), regardless of the manufacturer of the implement.

    The aim of this thesis is to implement ISOBUS at Ålö’s ECU (Electronic Control Unit) so that it can present its functionalities to VT. The aim is to integrate a purchased third party commercial ISOBUS library on ECU. The amount of work to achieve ISOBUS compatibility without third party library shall be estimated, and if there is time the task shall also be carried out. An object pool based on Ålö’s existing interface shall be created, where the object pool is the graphical interface shown at VT. A demonstrator of ISOBUS VT shall be done.

    To implement the third party library hardware functions towards the CAN-bus was required. The hardware functions include receiving messages from a buffer and send messages directly on the bus. For the library to be alive and running it had to be initialized and a periodic call to the library had to be done. The result is that the library was implemented on ECU and data flows between ECU and VT.

    To achieve ISOBUS compatibility without third party library the existing protocol on Ålö’s ECU has to be removed by a base support for ISOBUS. Then a last part must be written to achieve full compatibility. Commands that the ISOBUS standard defines between ECU and VT has to be written, and callback functions that is called when VT sends commands to ECU. Management of answers and errors also have to be implemented. ISOBUS compatibility without third party library wasn’t carried out, but the amount of work was estimated and a general description of what has to be done is written. The conclusion is that it requires a lot of work and scrutiny of the standard. The advantage is that you get an insight into how the system works and the ability to influence functionalities yourself.

    The object pool design was based on Ålö’s existing interface. Menu systems was implemented, and a linear bar graph and a meter have the possibilities to show height and angle of the tractor loader bucket. Different ways to show a menu system has been discussed. The result is an object pool with the basic functions for Ålö’s interface, the demonstrator presents these functionalities. The interface for VT can be made quite similar to Ålö’s existing interface, with some differences such as fonts, image quality and menu functions.

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    Implementering av ISOBUS på ECU vid Ålö AB
  • 6. Eriksson, Lennart
    et al.
    Trygg, Johan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wold, Svante
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umetrics Inc., 42 Pine Hill Rd, Hollis, NH 03049, USA.
    PLS-trees (R), a top-down clustering approach2009In: Journal of Chemometrics, ISSN 0886-9383, E-ISSN 1099-128X, Vol. 23, no 11, p. 569-580Article in journal (Refereed)
    Abstract [en]

    A hierarchical clustering approach based on a set of PLS models is presented. Called PLS-Trees (R), this approach is analogous to classification and regression trees (CART), but uses the scores of PLS regression models as the basis for splitting the clusters, instead of the individual X-variables. The split of one cluster into two is made along the sorted first X-score (t(1)) of a PLS model of the cluster, but may potentially be made along a direction corresponding to a combination of scores. The position of the split is selected according to the improvement of a weighted combination of (a) the variance of the X-score, (b) the variance of Y and (c) a penalty function discouraging an unbalanced split with very different numbers of observations. Cross-validation is used to terminate the branches of the tree, and to determine the number of components of each cluster PLS model. Some obvious extensions of the approach to OPLS-Trees and trees based on hierarchical PLS or OPLS models with the variables divided in blocks depending on their type, are also mentioned. The possibility to greatly reduce the number of variables in each PLS model on the basis of their PLS w-coefficients is also pointed out. The approach is illustrated by means of three examples. The first two examples are quantitative structure-activity relationship (QSAR) data sets, while the third is based on hyperspectral images of liver tissue for identifying different sources of variability in the liver samples.

  • 7.
    Fällman, Daniel
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Mediated reality through glasses or binoculars? Exploring use models of wearable computing in the context of aircraft maintenance.2003In: International Journal of Human-Computer Interaction, ISSN 1044-7318, E-ISSN 1532-7590, Vol. 15, no 2, p. 265-284Article in journal (Refereed)
    Abstract [en]

    Aircraft maintenance is often considered a typical application for specialized wearable computer systems, designed and used for a specific purpose only. From the findings of an interpretive case study conducted at Scandinavian Airlines Systems, the largest commercial airline in Scandinavia, there is evidence to question the potential usefulness of such a system.

    Instead, in this article, aircraft maintenance is used to explore the potentialities of different use models of wearable computing (i.e., the way the system is designed, used, and understood, and which should also make sense in other environments). The use models are (a) a vertical model addressed by a binoculars-analogy, where the system is designed and used for a specific purpose; and (b) a horizontal model, approached by perceiving wearable computers as eyeglasses, where the system is used throughout the day for a number of activities. Problems with both models suggest an alternative use model, which is presented as the embodied use model, drawing on the notion of embodiment introduced by Ihde (1990).

  • 8.
    Hjort, Andrej
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Prototyp för analys av körteknik med motorcykel2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Mikroelektromekaniska system eller MEMS, används i allt större utsträcknining i fordon för att samla mätresultat om vinkel samt acceleration som sedan kan användas i samband med andra system i fordonet för ökad säkerhet och stabilitet. I bilar har smarta system använts sedan länge för airbag-system och ABS bromsar. Då just MEMS-sensorer har fördelar som pris, storlek och tillgänglighet ses allt fler möjligheter även för utveckling kring motorcyklar. Målet med detta projekt har varit att ta fram en prispressad och lite enklare produkt där föraren kan se information om sin lutning och acceleration med hjälp av en accelerometer och gyroskop . Tester har gjorts med produkten fastmonterad på motorcykel på data såsom lutning och acceleration efter ett så kallat komplementärfilter. Detta har gjorts för att se vilka värden på filtret som fungerar bäst för en eventuell färdig produkt. Utifrån testerna kan man utgöra att motorvibrationer har en påverkan för mätning av acceleration och vinkel. Dessa minskar i viss mån med vibrationsdämpande lösningar såsom gummiupphängningar men för att kunna få ut mätbara värden implementeras ett mjukvaru lågpassfilter samt ett komplementärfilter.

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  • 9.
    Jonsson, Isak
    Umeå University, Faculty of Science and Technology, Computing Science.
    Recursive Blocked Algorithms, Data Structures, and High-Performance Software for Solving Linear Systems and Matrix Equations2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the development of efficient and reliable algorithms and library software for factorizing matrices and solving matrix equations on high-performance computer systems. The architectures of today's computers consist of multiple processors, each with multiple functional units. The memory systems are hierarchical with several levels, each having different speed and size. The practical peak performance of a system is reached only by considering all of these characteristics. One portable method for achieving good system utilization is to express a linear algebra problem in terms of level 3 BLAS (Basic Linear Algebra Subprogram) transformations. The most important operation is GEMM (GEneral Matrix Multiply), which typically defines the practical peak performance of a computer system. There are efficient GEMM implementations available for almost any platform, thus an algorithm using this operation is highly portable.

    The dissertation focuses on how recursion can be applied to solve linear algebra problems. Recursive linear algebra algorithms have the potential to automatically match the size of subproblems to the different memory hierarchies, leading to much better utilization of the memory system. Furthermore, recursive algorithms expose level 3 BLAS operations, and reveal task parallelism. The first paper handles the Cholesky factorization for matrices stored in packed format. Our algorithm uses a recursive packed matrix data layout that enables the use of high-performance matrix--matrix multiplication, in contrast to the standard packed format. The resulting library routine requires half the memory of full storage, yet the performance is better than for full storage routines.

    Paper two and tree introduce recursive blocked algorithms for solving triangular Sylvester-type matrix equations. For these problems, recursion together with superscalar kernels produce new algorithms that give 10-fold speedups compared to existing routines in the SLICOT and LAPACK libraries. We show that our recursive algorithms also have a significant impact on the execution time of solving unreduced problems and when used in condition estimation. By recursively splitting several problem dimensions simultaneously, parallel algorithms for shared memory systems are obtained. The fourth paper introduces a library---RECSY---consisting of a set of routines implemented in Fortran 90 using the ideas presented in paper two and three. Using performance monitoring tools, the last paper evaluates the possible gain in using different matrix blocking layouts and the impact of superscalar kernels in the RECSY library.

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  • 10.
    Kampik, Timotheus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Signavio GmbH, Berlin, Germany.
    Najjar, Amro
    Umeå University, Faculty of Science and Technology, Department of Computing Science. AI-Robolab/ICR, Computer Science and Communications, University of Luxembourg, Esch-sur-Alzette, Luxembourg.
    Integrating Multi-agent Simulations into Enterprise Application Landscapes2019In: Highlights of Practical Applications of Survivable Agents and Multi-Agent Systems: The PAAMS Collection. PAAMS 2019 / [ed] De La Prieta F. et al., 2019, p. 100-111Conference paper (Refereed)
    Abstract [en]

    To cope with increasingly complex business, political, and economic environments, agent-based simulations (ABS) have been proposed for modeling complex systems such as human societies, transport systems, and markets. ABS enable experts to assess the influence of exogenous parameters (e.g., climate changes or stock market prices), as well as the impact of policies and their long-term consequences. Despite some successes, the use of ABS is hindered by a set of interrelated factors. First, ABS are mainly created and used by researchers and experts in academia and specialized consulting firms. Second, the results of ABS are typically not automatically integrated into the corresponding business process. Instead, the integration is undertaken by human users who are responsible for adjusting the implemented policy to take into account the results of the ABS. These limitations are exacerbated when the results of the ABS affect multi-party agreements (e.g., contracts) since this requires all involved actors to agree on the validity of the simulation, on how and when to take its results into account, and on how to split the losses/gains caused by these changes. To address these challenges, this paper explores the integration of ABS into enterprise application landscapes. In particular, we present an architecture that integrates ABS into cross-organizational enterprise resource planning (ERP) processes. As part of this, we propose a multi-agent systems simulator for the Hyperledger blockchain and describe an example supply chain management scenario type to illustrate the approach.

  • 11.
    Karlsson, Lars
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tisseur, Francoise
    Algorithms for Hessenberg-Triangular Reduction of Fiedler Linearization of Matrix Polynomials2015In: SIAM Journal on Scientific Computing, ISSN 1064-8275, E-ISSN 1095-7197, Vol. 37, no 3, p. C384-C414Article in journal (Refereed)
    Abstract [en]

    Small- to medium-sized polynomial eigenvalue problems can be solved by linearizing the matrix polynomial and solving the resulting generalized eigenvalue problem using the QZ algorithm. The QZ algorithm, in turn, requires an initial reduction of a matrix pair to Hessenberg-triangular (HT) form. In this paper, we discuss the design and evaluation of high-performance parallel algorithms and software for HT reduction of a specific linearization of matrix polynomials of arbitrary degree. The proposed algorithm exploits the sparsity structure of the linearization to reduce the number of operations and improve the cache reuse compared to existing algorithms for unstructured inputs. Experiments on both a workstation and a high-performance computing system demonstrate that our structure-exploiting parallel implementation can outperform both the general LAPACK routine DGGHRD and the prototype implementation DGGHR3 of a general blocked algorithm.

  • 12.
    Linde, Mattias
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Multi-core scalability measurements: issues and solutions2013In: Applied Parallel and Scientific Computing: 11th International Conference, PARA 2012, Helsinki, Finland, June 10-13, 2012, Revised Selected Papers / [ed] Pekka Manninen, Per Öster, Springer Berlin/Heidelberg, 2013, p. 319-327Conference paper (Refereed)
    Abstract [en]

    We discuss how power management development in multi-core processors to achieve higher performance using automatic frequency scaling can cause artifacts when doing performance comparisons and give pessimistic efficiency estimates for algorithms. Overclocking also causes underestimates of the theoretical peak performance of the CPU as can be seen in some cases on the TOP500 list. We show that overclocking capabilities, when available, must be taken into account in thread scheduling for better overall performance.

  • 13.
    Lindström, Johan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Webbaserad styrning av TV-apparater2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This project is based on a wish from the employees at Umeå Energi to have a solution for remote control of TV monitors in the office. The idea is a web-based solution to make it possible for the employees to open a web page and access basic functions on the four monitors in the office. The project has been done with the help of an old PC that works as an intermediary between the monitors and the users. The PC was running a webserver that could control functions on the monitors using scripts. The server was connected to the monitors through a serial interface (RS-232). All software being used was free and open, and most of the hardware Umeå Energi already had on site, thus costs have remained low. The final solution was a Linux-based server with Ubuntu and Apache, and the scripts used Bash code. A USB hub and four USB-to-serial adapters were used to connect the monitors to the server. All basic functions worked as intended, except that commands sometimes had to be applied twice by pressing the refresh button in the web browser. This is believed to have been caused by weak power supply to the USB hub.

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  • 14.
    Mehta, Amardeep
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Bayuh Lakew, Ewnetu
    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.
    Utility-based Allocation of Industrial IoT Applications in Mobile Edge Clouds2018In: 2018 IEEE 37th International Performance Computing and Communications Conference (IPCCC), IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    Mobile Edge Clouds (MECs) create new opportunities and challenges in terms of scheduling and running applications that have a wide range of latency requirements, such as intelligent transportation systems, process automation, and smart grids. We propose a two-tier scheduler for allocating runtime resources to Industrial Internet of Things (IIoT) applications in MECs. The scheduler at the higher level runs periodically - monitors system state and the performance of applications - and decides whether to admit new applications and migrate existing applications. In contrast, the lower-level scheduler decides which application will get the runtime resource next. We use performance based metrics that tells the extent to which the runtimes are meeting the Service Level Objectives (SLOs) of the hosted applications. The Application Happiness metric is based on a single application's performance and SLOs. The Runtime Happiness metric is based on the Application Happiness of the applications the runtime is hosting. These metrics may be used for decision-making by the scheduler, rather than runtime utilization, for example. We evaluate four scheduling policies for the high-level scheduler and five for the low-level scheduler. The objective for the schedulers is to minimize cost while meeting the SLO of each application. The policies are evaluated with respect to the number of runtimes, the impact on the performance of applications and utilization of the runtimes. The results of our evaluation show that the high-level policy based on Runtime Happiness combined with the low-level policy based on Application Happiness outperforms other policies for the schedulers, including the bin packing and random strategies. In particular, our combined policy requires up to 30% fewer runtimes than the simple bin packing strategy and increases the runtime utilization up to 40% for the Edge Data Center (DC) in the scenarios we evaluated.

  • 15.
    Moritz, Monica
    Umeå University, Faculty of Teacher Education, Mathematics, Technology and Science Education.
    Provkonstruktion för nätet: Validerat med Bloom´s reviderade taxonomi2007Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Att skapa rättvisa prov är något av det svåraste som finns för alla lärare. Denna rapport redogör för ett undervisningsförsök i att praktiskt använda Bloom´s reviderade taxonomi för att validera frågorna till ett prov, som byggs upp för och genomförs på dator. Undersöknings-gruppen utgörs av mina elever som läser kursen programmering A på gymnasienivå. En norsk undersökning har tidigare visat att pojkars provresultat höjs om proven utförs på dator, vilket också visade sig bli resultatet i min undersökning. Men till skillnad från den norska undersökningen så ökade också flickornas resultat i min undersökning. Med hjälp av denna teknik att skapa prov, skulle det vara enkelt och möjligt att skapa nationella datorbaserade prov inom flera olika kurser som skulle kunna vara till hjälp för lärare ute i landet att hitta rätt kunskapsnivå på kurserna.

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  • 16.
    Nilsson, Peter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Reveman, David
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Glitz: hardware accelerated image compositing using OpenGL2004In: USENIX association proceedings of the FREENIX track, 2004 USENIX annual technical conference, Berkeley: USENIX - The Advanced Computing Systems Association, 2004, p. 29-40Conference paper (Refereed)
    Abstract [en]

    In recent years 2D graphics applications and window systems tend to use more demanding graphics features such as alpha blending, image transformations and anti-aliasing. These features contribute to the user interfaces by making it possible to add more visual effects as well as new usable functionalities. All together it makes the graphical interface a more hospitable, as well as efficient, environment for the user. Even with today's powerful computers these tasks constitute a heavy burden on the CPU. This is why many proprietary window systems have developed powerful 2D graphics engines to carry out these tasks by utilizing the acceleration capabilities in modem graphics hardware. We present Glitz, an open source implementation of such a graphics engine, a portable 2D graphics library that can be used to render hardware accelerated graphics. Glitz is layered on top of OpenGL and is designed to act as an additional backend for cairo, providing it with hardware accelerated output. Further-more, an effort has been made to investigate if the level of hardware acceleration provided by the X Window System can be improved by using Glitz to carry out its fundamental drawing operations.

  • 17.
    Ojeda-May, Pedro
    et al.
    Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N). Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nam, Kwangho
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas 76019-0065, United States.
    Acceleration of Semiempirical QM/MM Methods through Message Passage Interface (MPI), Hybrid MPI/Open Multiprocessing, and Self-Consistent Field Accelerator Implementations2017In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 13, no 8, p. 3525-3536Article in journal (Refereed)
    Abstract [en]

    The strategy and implementation of scalable and efficient semiempirical (SE) QM/MM methods in. CHARMM are described. The serial version of the code was first profiled to identify routines that required parallelization. Afterward, the code was parallelized and accelerated with three approaches. The first approach was the parallelization of the entire QM/MM routines, including the Fock matrix diagonalization routines, using the CHARMM message passage interface (MPI) machinery. In the second approach, two different self-consistent.field (SCF) energy convergence accelerators were implemented using density and Pock matrices as targets for their extrapolations in the SCF procedure. In the third approach, the entire QM/MM and MM energy routines were accelerated by implementing the hybrid MPI/open multiprocessing (OpenMP) model in which both the task- and loop-leveL parallelitation strategies were adopted to balance loads between different OpenMP threads. The present implementation was tested on two solvated enzyme systems (including <100 QM atoms) and an S(N)2 symmetric reaction in water. The-MPI version exceeded existing SE QM methods in CHARMM which include the SCC-DFTB and SQUANTUM methods by at least 4-fold. The use of SCF convergence accelerators further accelerated,the code by similar to 12-35% depending on the size of the QM region and the number of CPU cores used. Although the MPI version displayed good scalability, the performance was diminished for large numbers of MPI processes due to the overhead associated with MPI communications between nodes. This issue was partially overcome by the hybrid MPI/OpenMP approach which displayed a better scalability for a larger number of CPU cores (up to 64 CPUs in the tested systems).

  • 18.
    Rezk, Nesma
    et al.
    Halmstad University.
    Purnaprajna, Madhura
    Amrita School of Engineering: Bangalore, Karnataka, India.
    Nordström, Tomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ul-Abdin, Zain
    Halmstad University.
    Recurrent Neural Networks: An Embedded Computing Perspective2020In: IEEE Access, E-ISSN 2169-3536, Vol. 81, no 1, p. 57967-57996Article in journal (Refereed)
    Abstract [en]

    Recurrent Neural Networks (RNNs) are a class of machine learning algorithms used for applications with time-series and sequential data. Recently, there has been a strong interest in executing RNNs on embedded devices. However, difficulties have arisen because RNN requires high computational capability and a large memory space. In this paper, we review existing implementations of RNN models on embedded platforms and discuss the methods adopted to overcome the limitations of embedded systems. We will define the objectives of mapping RNN algorithms on embedded platforms and the challenges facing their realization. Then, we explain the components of RNN models from an implementation perspective. We also discuss the optimizations applied to RNNs to run efficiently on embedded platforms. Finally, we compare the defined objectives with the implementations and highlight some open research questions and aspects currently not addressed for embedded RNNs. Overall, applying algorithmic optimizations to RNN models and decreasing the memory access overhead is vital to obtain high efficiency. To further increase the implementation efficiency, we point up the more promising optimizations that could be applied in future research. Additionally, this article observes that high performance has been targeted by many implementations, while flexibility has, as yet, been attempted less often. Thus, the article provides some guidelines for RNN hardware designers to support flexibility in a better manner.

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  • 19.
    Risberg, Emil
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Front loader task automation with distance measurement2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Front loaders are used in many agricultural applications. They are used in daily tasks that are performed by operators. The operator uses multiple different front loader equipment carrying out tasks, which are more or less repetitive. A common thing between these tasks even though different equipment is used, is that the working cycle is similar.

    A working cycle consists of multiple sequences. One of them involves loader control for desired object handling. If that part of the working cycle could be automated it could reduce the workload and operator stress, which would increase an operator’s daily working capacity.

    The aim with the thesis is to research the possibility to automate a part of the front loader working cycle. The goal is to create a prototype that can be used to automate the loader control part of the working cycle. The prototype will be implemented on a front loader for testing of a working cycle.

    To achieve the aim and goal, work will include research about which sensor technology that is best suited for the prototype. It will also include tests to see if there is a difference in accuracy when using a cheap or an expensive sensor and if it is possible to automate a part of the front loader working cycle.

    A sensor analysis was made and the ultrasonic sensor technology was chosen for the prototype. One expensive prototype sensor and one cheap extra sensor for comparison testing were chosen. Software was written for the sensors and they were tested on a test bench. The prototype was implemented on a front loader for test of a working cycle.

    The prototype can measure distance and send the required commands based on that. This indicates that it is possible to automate a part of the front loader working cycle.

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  • 20.
    Stenman, Johan
    Umeå University, Faculty of Teacher Education, Interactive Media and Learning.
    Den interaktiva tavlan: En studie av dess användningsområde i två undersökta skolor2005Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    I detta arbete belyser jag den interaktiva tavlans användningsområde i två svenska skolor, samt beskriver hur den används i andra länder som exempelvis Storbritannien. Syftet var även att undersöka på vilka punkter den skiljde sig från en vanlig whiteboard och även vilka problem som kunde uppstå vid användningen av den interaktiva tavlan i undervisningen. Undersökningen i de svenska skolorna genomfördes i form av en intervju med sex lärare som alla använde den interaktiva tavlan i sin undervisning. Kontakten med lärarna inleddes via brevväxling per e-post och avslutades med en telefonintervju.

    Resultatet visar att den interaktiva tavlan främst användes till att visa bilder och animationer som ett komplement till skolans traditionella whiteboard eftersom den interaktiva tavlan kändes för onaturlig att skriva på. Alla lärare i undersökningen betonade dock att den interaktiva tavlan fått ett positivt mottagande av eleverna, där interaktiviteten och användningen av bilder och ljud som tillfördes till undervisningen sågs som den största styrkan tillsammans med möjligheten att kunna stå framför klassen och styra datorn. Hälften av lärarna påpekade att de svårigheter som uppstått med den interaktiva tavlan lätt kan härledas till deras bristande teknikkunskaper. De anser därför att en utbildningskurs för att utvidga kunskaperna om tavlans funktioner är nödvändig, samt tillgången till teknisk support ifall utrustningen skulle drabbas av problem. Detta anser jag vara den största begränsningen med den interaktiva tavlan, de problem som eventuellt kan uppstå måste kunna avhjälpas för att tavlan skall kunna användas obehindrat i undervisningen.

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  • 21. Tärneberg, William
    et al.
    Mehta, Amardeep
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Wadbro, Eddie
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Eker, Johan
    Kihl, Maria
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Dynamic application placement in the Mobile Cloud Network2017In: Future generations computer systems, ISSN 0167-739X, E-ISSN 1872-7115, Vol. 70, p. 163-177Article in journal (Refereed)
    Abstract [en]

    To meet the challenges of consistent performance, low communication latency, and a high degree of user mobility, cloud and Telecom infrastructure vendors and operators foresee a Mobile Cloud Network that incorporates public cloud infrastructures with cloud augmented Telecom nodes in forthcoming mobile access networks. A Mobile Cloud Network is composed of distributed cost- and capacityheterogeneous resources that host applications that in turn are subject to a spatially and quantitatively rapidly changing demand. Such an infrastructure requires a holistic management approach that ensures that the resident applications’ performance requirements are met while sustainably supported by the underlying infrastructure. The contribution of this paper is three-fold. Firstly, this paper contributes with a model that captures the cost- and capacity-heterogeneity of a Mobile Cloud Network infrastructure. The model bridges the Mobile Edge Computing and Distributed Cloud paradigms by modelling multiple tiers of resources across the network and serves not just mobile devices but any client beyond and within the network. A set of resource management challenges is presented based on this model. Secondly, an algorithm that holistically and optimally solves these challenges is proposed. The algorithm is formulated as an application placement method that incorporates aspects of network link capacity, desired user latency and user mobility, as well as data centre resource utilisation and server provisioning costs. Thirdly, to address scalability, a tractable locally optimal algorithm is presented. The evaluation demonstrates that the placement algorithm significantly improves latency, resource utilisation skewness while minimising the operational cost of the system. Additionally, the proposed model and evaluation method demonstrate the viability of dynamic resource management of the Mobile Cloud Network and the need for accommodating rapidly mobile demand in a holistic manner.

  • 22.
    Wikstrand, Greger
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Nilsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Dougherty, Mark S
    Prioritized repeated eliminations multiple access: a novel protocol for wireless networksManuscript (preprint) (Other academic)
1 - 22 of 22
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