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  • 201.
    Blum, Johannes
    et al.
    University of Würzburg.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Language Theoretic Properties of Regular DAG Languages2019In: Information and Computation, ISSN 0890-5401, E-ISSN 1090-2651, Vol. 265, p. 78p. 57-76Article in journal (Refereed)
    Abstract [en]

    We study sets of directed acyclic graphs, called regular DAG languages, which are accepted by a recently introduced type of DAG automata motivated by current developments in natural language processing. We prove (or disprove) closure properties, establish pumping lemmata, characterize finite regular DAG languages, and show that "unfolding" turns regular DAG languages into regular tree languages, which implies a linear growth property and the regularity of the path languages of regular DAG languages. Further, we give polynomial decision algorithms for the emptiness and finiteness problems, and show that deterministic DAG automata can be minimized and tested for equivalence in polynomial time.

  • 202.
    Blum, Johannes
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Drewes, Frank
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Properties of Regular DAG Languages2016In: Proc. 10th International Conference on Language and Automata Theory and Applications (LATA 2016) / [ed] A.H. Dediu, J. Janoušek, C. Martín-Vide, and B. Truthe, Springer Publishing Company, 2016, p. 427-438Conference paper (Refereed)
    Abstract [en]

    A DAG is a directed acyclic graph. We study the properties of DAG automata and their languages, called regular DAG languages. In particular, we prove results resembling pumping lemmas and show that the finiteness problem for regular DAG languages is in P.

  • 203.
    Blusi, Madeleine
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Occupational Therapy.
    Nilsson, Ingeborg
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Occupational Therapy.
    Lindgren, Helena
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Older adults co-creating meaningful individualized social activities online for healthy ageing2018In: Building continents of knowledge in oceans of data: The future of co-created eHealth / [ed] Adrien Ugon, Daniel Karlsson, Gunnar O. Klein, Anne Moen, IOS Press, 2018, Vol. 247, p. 775-779Chapter in book (Refereed)
    Abstract [en]

    Social isolation and loneliness among older people is a growing problem with negative effects on physical and mental health. In co-creation with older adults individualized social activities were designed where older adults through computer mediated communication were able to participate in social activities without leaving their homes. Four types of activities were designed; outdoor activity, music event, visiting a friend and leisure activity. A participatory action research design was applied, where end users together with scientists from two research fields developed, tested and evaluated online participation in the activities. Usability and safety of the systems were major concerns among older adults. The evaluation pointed out that level of simplicity, usability and audio-video quality determined the level of satisfaction with the human interaction during the activity, thereby affecting the meaningfulness of the activity. The research presented in this paper constitutes the first step in a long-term research process aiming at developing a digital coaching system that gives older adults personalized support for increasing participation in meaningful social activities.

  • 204.
    Bodin, Kenneth
    et al.
    Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Lacoursière, Claude
    Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Servin, Martin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Constraint Fluids2012In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 18, no 3, p. 516-526Article in journal (Refereed)
    Abstract [en]

    We present a fluid simulation method whereincompressibility is enforced through a holonomic constrainton the mass density. The method starts in aLagrangian particle formulation where the mass densityand other field quantities are represented by SmoothedParticle Hydrodynamics (SPH) kernel approximations.The density constraint is formulated as a regularizedmanybody constraint and is equivalent to very highsound speed. The system is integrated using a variationaldiscrete-time scheme, SPOOK, that includesconstraint regularization and stabilization. This constraintformulation of SPH enables systematic multiphysicsintegration, between rigid multibody physicsand fluids, where buoyancy falls out naturally. The fluidmodel results in a linear system of equations, whilemore general multiphysics systems result in a mixedlinear complementarity problem (MLCP) and we solvethese using iterative methods. The results demonstratenear perfect incompressibility, vastly improved stability,allowing for large time steps, and two orders of magnitudeimproved computational performance. Proof ofconcept is given for computer graphics applications andinteractive simulations.

  • 205.
    Bodin, Tora
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Expected later information access invites shorter reading time and possible comprehension loss2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    With the increased use of technology in society, there are concerns about how reading is affected by the constant access to an incessantly increasing amount of information. The present study examined how reading strategies and resulting memory and comprehension is affected by the belief that information to be remembered would continue to be available. In a within- participant experiment, twenty-seven participants were instructed to read six texts, and led to believe that they would have access to some of the texts while later answering comprehension questions. The results showed that participants spent significantly longer time reading texts they believed would not be accessible later, compared to those they believed they would have access to (p= .0007, d = 0.47). The participants did achieve slightly higher scores on the comprehension questions for the texts they believed they would not have access to, compared to the other condition, but the effect was not significant. The findings have implications for potential changes to reading strategies in response to increased use of technology as an external memory and information storage. I discuss how these strategies could have affected the raise of Fake News, inasmuch as increased information load from the Internet leads to a less meticulous reading style.

  • 206.
    Bodén, Johan
    et al.
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Jegers, Kalle
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Lidström, Mattias
    Wiberg, Charlotte
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Wiberg, Mikael
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Point or click?: Evaluating two input modalities for mobile games2007In: Proceedings of the Second International Conference on Internet and Web Applications and Services, 2007Conference paper (Refereed)
    Abstract [en]

    Previous research in computer games have focused on user experience from the perspectives of game content, graphics, interactivity and underling game story while missing to address the effect of a certain input modality on the user experience. In this paper we report from two user studies that focus on players' experience and performance in relation to the use of two different input modalities for the same game and whether it changes the flow and gameplay in any way. The overall research was according to this whether a game can be more fun to play with a certain input modality? The paper presents the results from these studies and draws conclusions based on these data in relation to computer games and user experiences in the context of mobile game playing.

  • 207.
    Bodén, Johan
    et al.
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Wiberg, Charlotte
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    iBalance - a cross-media service platform2007In: CMID'07 / [ed] Wiberg, C. & Wiberg M., 2007Conference paper (Refereed)
  • 208.
    Bohlin, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Toward higher-order network models2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Complex systems play an essential role in our daily lives. These systems consist of many connected components that interact with each other. Consider, for example, society with billions of collaborating individuals, the stock market with numerous buyers and sellers that trade equities, or communication infrastructures with billions of phones, computers and satellites.

    The key to understanding complex systems is to understand the interaction patterns between their components - their networks. To create the network, we need data from the system and a model that organizes the given data in a network representation. Today's increasing availability of data and improved computational capacity for analyzing networks have created great opportunities for the network approach to further prosper. However, increasingly rich data also gives rise to new challenges that question the effectiveness of the conventional approach to modeling data as a network. In this thesis, we explore those challenges and provide methods for simplifying and highlighting important interaction patterns in network models that make use of richer data.

    Using data from real-world complex systems, we first show that conventional network modeling can provide valuable insights about the function of the underlying system. To explore the impact of using richer data in the network representation, we then expand the analysis for higher-order models of networks and show why we need to go beyond conventional models when there is data that allows us to do so. In addition, we also present a new framework for higher-order network modeling and analysis. We find that network models that capture richer data can provide more accurate representations of many real-world complex systems.

  • 209.
    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.

  • 210.
    Bohlin, Victor
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Visual Special Relativity2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Albert Einstein predicted in 1905 with his paper on special relativity the signi cantvisual eects of objects moving close to the speed of light. Einstein could not see them then but with todays graphical hardware it is possible to produce these eects in real time in a computer simulation. In this thesis the implementation, results and comparison of two techniques for doing this are presented. The two techniques dier substantially in how they execute the task. One alters the vertex positions of the objects and the other performs the eects as a post process step using a cube map. The results of the two techniques are generally the same,both having dierent advantages and disadvantages.

  • 211.
    Bohm, Erik
    et al.
    Umeå University, Faculty of Social Sciences, Informatics.
    Appelvik, Christopher
    Umeå University, Faculty of Social Sciences, Informatics.
    Kreativitet och processtyrning: En studie om processtyrning som förändringsfaktor för individens kreativitet2008Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Systemutveckling påverkas till viss del av olika former av processtyrning. Det kan handla om rena systemutvecklingsmetoder men kan även innefatta mer subtila former av styrningar som till exempel tidspress, ekonomiska styrningar och styrningar i termer av tekniska verktyg. Styrande faktorer som nämns ovan påverkar individens förutsättningar för att verka kreativt i sitt arbete och olika typer av styrande faktorer påverkar individens kreativitet på olika sätt. De mer individnära processtyrningarna som främst påverkar individens arbetsglädje och motiva-tion vilket i sin tur påverkar kreativiteten går att sätta i en kategori. Dessutom existerar en annan kategori som innefattar de styrningar som i större utsträckning rör verksamhetens hel-het och är något svårare att påverka. Syftet med uppsatsen är att åskådliggöra hur olika grader av processtyrning påverkar individens kreativitet. Med hjälp av en fallstudie som genomförts på två olika systemutvecklingsföretag har vi kunnat identifiera skillnader mellan olika typer av kreativitet samt vad som påverkar vilken typ av kreativitet eller kreativitetspåverkande faktorer. Resultatet av vår studie är att just kreativitetspåverkande faktorer som arbetsglädje och motivation påverkas i större utsträckning av processtyrning än vad kreativitet i sig gör. Trots det faktum att individen är medveten om, och har identifierat, olika typer av processtyr-ning står det klart att hon kan vara kreativ i den miljö där hon verkar när de kreativitetspåverkande faktorerna har en hög uppfyllelse.

  • 212.
    Boketoft, Carl-Ola
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Web Content ManagementSystem Powered by Ajax2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis is about the development of a web site for three restaurants in South Korea. For the maintenance and updating of the contents of the web site a CMS (Content Management System) was developed. The major part of the work was conducted in South Korea and in close collaboration with the owners of the restaurants in order to improve communication possibilities and to be able to gather materials for the project.A theoretical study was conducted to acquire knowledge about the web development technique Ajax, both from a programming view and how to use it for improving usability of the web site functions.From the results of the theoretical study, methods were chosen and applied into a detailed conceptual model of the web site. This model was used as a base for the implementation of the web site pages and content management functions.The resulting implementation of the web site is based on a common structure for the dierent pages, with contents available in both English and Korean. The updating of the contents is done by Ajax enhanced functions in the CMS, which also contains functions for image uploading, text editing, and layout management.

  • 213.
    Bonemark, Oscar
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Success factors for e-sport games2013In: Proceedings of Umeå's 16th student conference in computing science: USCCS 2013 / [ed] Suna Bensch & Frank Drewes, Umeå: Umeå universitet , 2013, p. 1-12Conference paper (Other academic)
    Abstract [en]

    Some multiplayer video games rise to become successful inthe field of e-sports. This paper tries to find out why this is the case.We compare a set of seven video game properties with six establishede-sport games in an attempt to find out whether there are propertiesof multiplayer video games that all established e-sport games have incommon.

  • 214. Bontsema, Jan
    et al.
    Hemming, Jochen
    Pekkeriet, Erik
    Saeys, Wouter
    Edan, Yael
    Shapiro, Amir
    Hočevar, Marko
    Oberti, Roberto
    Armada, Manuel
    Ulbrich, Heinz
    Baur, Jörg
    Debilde, Benoit
    Best, Stanley
    Evain, Sébastien
    Gauchel, Wolfgang
    Hellström, Thomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ringdahl, Ola
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    CROPS: Clever Robots for Crops2015In: Engineering & Technology Reference, ISSN 2056-4007, Vol. 1, no 1Article in journal (Refereed)
    Abstract [en]

    In the EU-funded CROPS project robots are developed for site-specific spraying and selective harvesting of fruit and fruit vegetables. The robots are being designed to harvest crops, such as greenhouse vegetables, apples, grapes and for canopy spraying in orchards and for precision target spraying in grape vines. Attention is paid to the detection of obstacles for autonomous navigation in a safe way in plantations and forests. For the different applications, platforms were built. Sensing systems and vision algorithms have been developed. For software the Robot Operating System is used. A 9 degrees of freedom manipulator was designed and tested for sweet-pepper harvesting, apple harvesting and in close range spraying. For the applications different end-effectors were designed and tested. For sweet pepper a platform that can move in between the crop rows on the common greenhouse rail system which also serves as heating pipes was built. The apple harvesting platform is based on a current mechanical grape harvester. In discussion with growers so-called ‘walls of fruit trees’ have been designed which bring robots closer to the practice. A canopy-optimised sprayer has been designed as a trailed sprayer with a centrifugal blower. All the applications have been tested under practical conditions.

  • 215.
    Borg, Andreas
    et al.
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Fredriksson, Jonas
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Gunnarsson, August
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Effektiv kravställning i små organisationer: En experimentell fallstudie i en liten organisation2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Incorrect requirements have long been considered to be one of the biggest reasons for failed IT projects. Insufficient requirements are also one of the most expensive sources of error. This is especially problematic within small enterprises, which in nature are time and cost sensitive. The purpose of this experimental case study is to identify efficient requirements gathering activities and by extension an efficient requirements gatherings process for small enterprises by utilizing their unique prerequisites. We gathered data through the execution of five user-centered requirements gathering activities on a small organization. The result of these activities, our observations and a survey were analyzed in order to draw conclusions regarding the success and efficiency of the activities and process as a whole. The results show that by utilizing the prerequisites of small organizations through the use of user-centered activities an efficient requirements gathering process can be accomplished. The results also show that the prerequisites of small organizations combined with the impact of external consultants with the purpose of problematizing the operational procedures contributes to other organizational benefits than the requirements documentation. 

  • 216.
    Boström, Erik
    et al.
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Celik, Onur Can
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Towards a Maturity Model for Digital Strategizing: A qualitative study of how an organization can analyze and assess their digital business strategy2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Many  companies  are  struggling  to  navigate  in  the  rapidly  changing  environment  and uncertain time of the digital era. Previous research has been exploring the ongoing trend of digital transformation, as well as digital business strategies, but still there is little guidance for  practitioners  in  terms  of  concrete  frameworks  and  concepts  for  digital  business strategizing.  This  thesis  investigates  critical  factors  of  digital  business  strategizing  and contributes  by  developing  a  maturity  model  for  digital  business  strategizing.  The contribution  of  this  study  is  two  folded,  on  the  one  hand  it  provides  practitioners  a conceptual  artefact  in  order  to  analyze  their  challenges  in  the  new  landscape  of  digital transformation and on the other it gives valuable insights for researchers on the new rising phenomena of digital business strategies.

  • 217. Brasselet, Romain
    et al.
    Johansson, Roland S
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Arleo, Angelo
    Isometric coding of spiking haptic signals by peripheral somatosensory2011In: Advances in Computational Intelligence: 11th international work-conference on artificial neural networks, IWANN 2011, Torremolinos-Málaga, Spain, June 8-10, 2011, Proceedings, Part I / [ed] Cabestany, J; Rojas, I; Joya, G, Berlin: Springer Berlin/Heidelberg, 2011, p. 528-536Conference paper (Refereed)
    Abstract [en]

    We study how primary tactile afferents encode relevant contact features to mediate early processing of haptic information. In this paper, we apply metrical information theory to perform temporal decoding of human microneurography data. First, we enrich the theory by deriving a novel spike train metrics inspired by neuronal computation. This spike train metrics can be interpreted biologically and its behaviour is not influenced by spontaneous activity, which decreases the ability of other spike metrics to separate input patterns. Second, we employ our metrical information tools to demonstrate that primary spiking signals allow a putative neural decoder to go beyond stimulus discrimination. They transmit information about geometrical properties of the input space. We show that first-spike latencies are enough to guarantee maximum information transmission of tactile stimuli. However, entire primary spike trains are necessary to encode isometric representations of the stimulus space, a likely basis for generalisation in haptic perception.

  • 218.
    Bratteteig, Tone
    et al.
    Design av informasjonssystemer, Universitet i Oslo.
    Wagner, Ina
    Institut für Gestaltungs- und Wirkungsforschung ,Technische Universität Wien.
    Morrison, Andrew
    Intermedia, Universitetet i Oslo.
    Stuedahl, Dagny
    Institutt for medier og kommunikasjon, Universitetet i Oslo.
    Mörtberg, Christina
    Umeå University, Faculty of Social Sciences, Department of Informatics. Design av informasjonssystemer, Universitet i Oslo.
    Research practices in digital design2010In: Exploring digital design: multi-disciplinary design practices / [ed] Wagner, Ina, Bratteteig, Tone, Stuedahl, Dagny, London: Springer London, 2010, p. 17-54Chapter in book (Other academic)
    Abstract [en]

    In the twenty-first century, we are literally surrounded by digital things and things that turn out to be digital – or have some digital parts or are parts of a larger system in which there are digital elements. We carry around mobile phones and watches; many also have additional music players, PDAs or PCs. We live in houses filled with digital networks and artefacts; we depend on infrastructures that are partly digital and have digital systems attached to them; we use public and private services that are digital, are based on digital infrastructures and have other digital systems attached to them; and we experience embedded, ubiquitous computing as we live in digitally enhanced environments that support our activities with or without our conscious control. The digital layer(s) in the world constitute a real world.

  • 219. Breitgand, D.
    et al.
    Maraschini, A.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Policy-Driven Service Placement Optimization in Federated Clouds2011Report (Other academic)
    Abstract [en]

    Efficient provisioning of elastic services constitutes a significant management challenge for cloud computing providers. We consider a federated cloud paradigm, where one cloud can subcontract workloads to partnering clouds to meet peaks in demand without costly over-provisioning. We propose a model for service placement in federated clouds to maximize profit while protecting Quality of Service (QoS) as specified in the Service Level Agreements (SLA) of the workloads. Our contributions include an Integer Linear Program (ILP) formulation of the generalized federated placement problem and application of this problem to load balancing and consolidation within a cloud, as well as for cost minimization for remote placement in partnering clouds. We also provide a 2-approximation algorithm based on a greedy rounding of a Linear Program (LP) relaxation of the problem. We implement our proposed approach in the context of the RESERVOIR architecture.

  • 220.
    Broström, Göran
    et al.
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Lindkvist, Marie
    Umeå University, Faculty of Social Sciences, Department of Statistics.
    Partial Partial Likelihood2008In: Communications in statistics. Simulation and computation, ISSN 0361-0918, E-ISSN 1532-4141, Vol. 37, no 4, p. 679-686Article in journal (Refereed)
    Abstract [en]

    The maximum likelihood and maximum partial likelihood approaches to the proportional hazards model are unified. The purpose is to give a general approach to the analysis of the proportional hazards model, whether the baseline distribution is absolutely continuous, discrete, or a mixture. The advantage is that heavily tied data will be analyzed with a discrete time model, while data with no ties is analyzed with ordinary Cox regression. Data sets in between are treated by a compromise between the discrete time model and Efron's approach to tied data in survival analysis, and the transitions between modes are automatic. A simulation study is conducted comparing the proposed approach to standard methods of handling ties. A recent suggestion, that revives Breslow's approach to tied data, is finally discussed.

  • 221.
    Brunberg, Marike
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    User optimized design of handheld medical devices -applications and casing2010Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
  • 222.
    Brundin, Karl
    et al.
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Gustavsson, Björn
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Säkeranvändbarhet: En studie om datorsäkerhet kontra användarvänlighet inom vården2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 223. Brush, Eleanor
    et al.
    Brännström, Åke
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics. Evolution and Ecology Program, International Institute for Applied Systems Analysis, Laxenburg, Austria.
    Dieckmann, Ulf
    Indirect reciprocity with negative assortment and limited information can promote cooperation2018In: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 443, p. 56-65Article in journal (Refereed)
    Abstract [en]

    Cooperation is ubiquitous in biological and social systems, even though cooperative behavior is often costly and at risk of exploitation by non-cooperators. Several studies have demonstrated that indirect reciprocity, whereby some members of a group observe the behaviors of their peers and use this information to discriminate against previously uncooperative agents in the future, can promote prosocial behavior. Some studies have shown that differential propensities of interacting among and between different types of agents (interaction assortment) can increase the effectiveness of indirect reciprocity. No previous studies have, however, considered differential propensities of observing the behaviors of different types of agents (information assortment). Furthermore, most previous studies have assumed that discriminators possess perfect information about others and incur no costs for gathering and storing this information. Here, we (1) consider both interaction assortment and information assortment, (2) assume discriminators have limited information about others, and (3) introduce a cost for information gathering and storage, in order to understand how the ability of discriminators to stabilize cooperation is affected by these steps toward increased realism. We report the following findings. First, cooperation can persist when agents preferentially interact with agents of other types or when discriminators preferentially observe other discriminators, even when they have limited information. Second, contrary to intuition, increasing the amount of information available to discriminators can exacerbate defection. Third, introducing costs of gathering and storing information makes it more difficult for discriminators to stabilize cooperation. Our study is one of only a few studies to date that show how negative interaction assortment can promote cooperation and broadens the set of circumstances in which it is know that cooperation can be maintained.

  • 224.
    Bryson, Joanna J.
    et al.
    University of Bath.
    Theodorou, Andreas
    Umeå University, Faculty of Science and Technology, Department of Computing Science. University of Bath, Bath, UK.
    How society can maintain human-centric artificial intelligence2019In: Human-centered digitalization and services / [ed] Marja Toivonen and Eveliina Saari, Springer, 2019, p. 305-323Chapter in book (Refereed)
    Abstract [en]

    Although not a goal universally held, maintaining human-centric artificial intelligence is necessary for society's long-term stability. Fortunately, the legal and technological problems of maintaining control are actually fairly well understood and amenable to engineering. The real problem is establishing the social and political will for assigning and maintaining accountability for artifacts when these artifacts are generated or used. In this chapter we review the necessity and tractability of maintaining human control and the mechanisms by which such control can be achieved. What makes the problem both most interesting and most threatening is that achieving consensus around any human-centered approach requires at least some measure of agreement on broad existential concerns.

    The full text will be freely available from 2021-06-04 11:17
  • 225.
    Brändström, Magnus
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Spelifikationers potentiella värdeskapande i projektarbete2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Digital games are today avaliable on all kinds of different platform. Games and game thinking is also increasingly being applied within non-traditional contexts. This thesis explores the term "gamifiation" which can be defined as "the use of game design elements in non-game contexts". The purpose of the study was to identify and give perspective on the discourse surrounding the use and applicability of the term today. More specifically, it explores the possibilities of the potentially value creating ability in the context of work, and focused on the application of gamified software in the context of project work. To understand the power in using game elements in non-game context, the field surrounding motivation in games is explored, as well as the discourse surrounding gamification. Through a qualitative survey using semi-structured interviews the potential use and value of gamification in the project context was investigated. Three approaches to gamification, a rejective, a commercial and an academic are presented. Self-determination theory is used to understand motivation in games.This and the insights resulting from the interviews, the survey of the field, and the theoretical understanding of project work are used to give a perspective on the use of game elements in project work. Among the recommendations are designing for a particular context and different user groups, connecting the use of interface elements with the users intrinsic needs for competence, autonomy and relatedness, using gamification as a part and not the focus of the design process, and adding percieved user values, or "fun" to motivate users. Gamification is suggested for appliance as a means to attract staff and clients to a project, motivating users to learn or achieve or motivating users to engage with the system in a certain way. 

  • 226.
    Brändström, Magnus
    et al.
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    Dueso Tejero, Albert
    Umeå University, Faculty of Social Sciences, Department of Informatics.
    How to encourage stretching and breaks at work: Understanding long term usage of a behaviour change support system2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    We are spending more and more time seated at work, which increases the risk for health problems. Behaviour change support systems that encourage breaks and stretching at work have been used as interventions to try to reduce these problems. No previous studies had looked at how these systems were used for long periods of time. In this qualitative study based on ten interviews, we aimed for expanding our understanding of long-term usage of such systems by studying one called ‘Efons’. The results indicate that the main factors influencing long-term usage are timely reminders, the impact that the stretching exercises has on the users’ health and the education of the user about health recommendations. We also found elements we argue have the ability to influence long-term usage and currently do not exist in the system studied or its context of use, such as adapt the system to the needs of the user or provide education about why these systems are useful.

  • 227.
    Brännström, Andreas
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Knowledge Elicitation of Human Activities Using a Graphical Modeling Language2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Recent, and ongoing, research has been addressing the general problem of representing complex human activities for the purpose to provide intelligent software agents with a way to identify, reason, and evaluate human activities. Reliable evaluation of complex human activities requires the intelligent agent to obtain a representation that comprises distinguishing features of an activity. This is a challenging task, since a person´s activity is driven by goals, motives, and norms that may be conflicting in a situation. In order to provide knowledge about human activities to an intelligent software agent, we require tools that can allow us modeling human activities enabling knowledge elicitation. This study has evaluated a software prototype of a graphical modeling language with the overall research question to find the minimum language elements required to elicit the knowledge of activities from a domain expert. Eight participants tested the prototype through think aloud usability sessions were their understanding of the structure of the language was tested. Qualitative data analysis was conducted using a Grounded theory approach, which validity has been discussed. The findings indicated that characteristics of the hierarchical structure of Activity Theory are a supportive theoretical framework for the graphical language that resembles the way occupational therapists reason when analyzing human activities. The study proposes a set of minimum elements for the graphical language. A focus a for future study is to target the intelligent software system to further expand and tune the language by the systems requirements.

  • 228.
    Brännström, Tomas
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    JavaScript and Web Integration of AgX Multiphysics Engine2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    JavaScript is the de facto language for client-side scripting on the web and has in recent years received a great boost in performance thanks to the `browser wars' where the different browser vendors compete to get higher market shares. AgX is a physics engine developed by Algoryx in Umeå, intended for use in simulations. This thesis explores possible methods of integrating JavaScript with AgX and in extension the possibility of integrating AgX into the web browser as a plugin, effectively enabling AgX for use in different web applications. Efforts were made to combine the embedded JavaScript API with the AgX browser plugin. This was found to be unfeasible for different reasons, although the AgX plugin as a separate piece of software was shown to work well.

  • 229.
    Brügger, Annina
    et al.
    University of Zurich, Switzerland.
    Richter, Kai-Florian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Fabrikant, Sara Irina
    University of Zurich, Switzerland.
    How does navigation system behavior influence human behavior?2019In: Cognitive Research: Principles and Implications, E-ISSN 2365-7464, Vol. 4, no 5Article in journal (Refereed)
    Abstract [en]

    Navigation systems are ubiquitous tools to assist wayfinders of the mobile information society with various navigational tasks. Whenever such systems assist with self-localization and path planning, they reduce human effort for navigating. Automated navigation assistance benefits navigation performance, but research seems to show that it negatively affects attention to environment properties, spatial knowledge acquisition, and retention of spatial information. Very little is known about how to design navigation systems for pedestrian navigation that increase both navigation performance and spatial knowledge acquisition. To this end, we empirically tested participants (N = 64) using four different navigation system behaviors (between-subject design). Two cognitive processes with varying levels of automation, self-localization and allocation of attention, define navigation system behaviors: either the system automatically executes one of the processes (high level of automation), or the system leaves the decision of when and where to execute the process to the navigator (low level of automation). In two experimental phases, we applied a novel empirical framework for evaluating spatial knowledge acquisition in a real-world outdoor urban environment. First, participants followed a route assisted by a navigation system and, simultaneously, incidentally acquired spatial knowledge. Second, participants reversed the route using the spatial knowledge acquired during the assisted phase, this time without the aid of the navigation system. Results of the route-following phase did not reveal differences in navigation performance across groups using different navigation system behaviors. However, participants using systems with higher levels of automation seemed not to acquire enough spatial knowledge to reverse the route without navigation errors. Furthermore, employing novel methods to analyze mobile eye tracking data revealed distinct patterns of human gaze behavior over time and space. We thus can demonstrate how to increase spatial knowledge acquisition without harming navigation performance when using navigation systems, and how to influence human navigation behavior with varying navigation system behavior. Thus, we provide key findings for the design of intelligent automated navigation systems in real-world scenarios.

  • 230.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Environmental Archaeology: Climate Change and E-Science2010In: Thule: Kungliga Skytteanska Samfundets Årsbok 2010, Umeå: Kungliga Skytteanska Samfundet , 2010, p. 55-69Chapter in book (Other academic)
  • 231.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab. Umeå University, Faculty of Arts, Humlab.
    SEAD - The Strategic Environmental Archaeology Database Inter-linking Multiproxy Environmental Data with Archaeological Investigations and Ecology2013In: Archaeology in the Digital Era: Papers from the 40th Annual Conference of Computer Applications and Quantitative Methods in Archaeology (CAA), Southampton, 26-29 March 2012 / [ed] Graeme Earl, Tim Sly, Angeliki Chrysanthi, Patricia Murrieta-Flores, Constantinos Papadopoulos, Iza Romanowska & David Wheatley, Amsterdam University Press, 2013, Vol. 1, p. 320-331Conference paper (Refereed)
    Abstract [en]

    The volume of data on past environmental and climate changes, as well as human interactions with these, has long since passed the level where it is manageable outside of large scale database systems. The Strategic Environmental Archaeology Database project aims to not only store and disseminate such data, but also provide tools for querying and analysing them, whilst maintaining a close connection with the archaeological and ecological data that are essential for their comprehensive interpretation. Large scale, geographically and chronologically unrestricted databases provide us with essentially unlimited scope for putting individual sites into a broader context and applying locally collated data to the investigation of earth system level changes. By providing integrated access to data from a variety of proxies, including plant macrofossils, pollen, insects and geochemistry, along with dating evidence, more complex questions can be answered where any single proxy would not be able to provide comprehensive answers.

  • 232.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    The Bugs Coleopteran Ecology Package (BugsCEP): the development and implementation of software for palaeoenvironmental and palaeoclimatological research2009Book (Other academic)
    Abstract [en]

    This book describes the development and practical application of a unique database orientated software package, BugsCEP, for environmental, climatic and biodiversity reconstruction from beetle assemblages. BugsCEP consists of a database of ecology and distribution data for over 9400 insect taxa, and includes temperature tolerance data for 436 species. It contains abundance and summary data for over 770 sites, most of the known European Quaternary fossil coleopteran record, supported by a bibliography of over 3700 sources. Built in statistics, including a specially developed habitat classification system, provide semi-quantitative environmental reconstructions to aid in the interpretation of sites. BugsCEP's querying and reporting functions also increase the efficiency with which analyses can be undertaken, including the facility to explore the fossil record of species by searching ecology and distribution data. The Mutual Climatic Range (MCR) reconstruction method is implemented and improved upon, including predictive modelling and the graphical output of reconstructions and climate space maps. BugsCEP is available from www.bugscep.com.

  • 233.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab. Umeå University, Faculty of Arts, Humlab.
    The Bugs Coleopteran Ecology Package (BugsCEP) database: 1000 sites and half a million fossils later2014In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 341, p. 272-282Article in journal (Refereed)
    Abstract [en]

    The Bugs database project started in the late 1980s as what would now be considered a relatively simple system, albeit advanced for its time, linking fossil beetle species lists to modern habitat and distribution information. Since then, Bugs has grown into a complex database of fossils records, habitat and distribution data, dating and climate reference data wrapped into an advanced software analysis package. At the time of writing, the database contains raw data and metadata for 1124 sites, and Russell Coope directly contributed to the analysis of over 154 (14%) of them, some 98790 identifications published in 231 publications. Such quantifications are infeasible without databases, and the analytical power of combining a database of modern and fossil insects with analysis tools is potentially immense for numerous areas of science ranging from conservation to Quaternary geology.

    BugsCEP, The Bugs Coleopteran Ecology Package, is the latest incarnation of the Bugs database project. Released in 2007, the database is continually added too and is available for free download from http://www.bugscep.com. The software tools include quantitative habitat reconstruction and visualisation, correlation matrices, MCR climate reconstruction, searching by habitat and retrieving, among other things, a list of taxa known from the selected habitat types. It also provides a system for entering, storing and managing palaeoentomological data as well as a number of expert system like reporting facilities.

    Work is underway to create an online version of BugsCEP, implemented through the Strategic Environmental Archaeology Database (SEAD) project (http://www.sead.se). The aim is to provide more direct access to the latest data, a community orientated updating system, and integration with other proxy data. Eventually, the tools available in the offline BugsCEP will be duplicated and Bugs will be entirely in the web.

    This paper summarises aspects of the current scope, capabilities and applications of the BugsCEP database and software, with special reference to and quantifications of the contributions of Russell Coope to the field of palaeoentomology as represented in the database. The paper also serves to illustrate the potential for the use of BugsCEP in biographical studies, and discusses some of the issues relating to the use of large scale sources of quantitative data.

    All datasets used in this article are available through the current version of BugsCEP available at http://www.bugscep.com.

  • 234.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab. Umeå University, Faculty of Arts, Humlab.
    Buckland, Paul C.
    BugsCEP, an entomological database twenty-five years on2014In: Antenna (Journal of the Royal Entomological Society), ISSN 0140-1890, Vol. 38, no 1, p. 21-28Article in journal (Refereed)
  • 235.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Eriksson, Erik J.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Palm, Fredrik
    Umeå University, Faculty of Arts, Humlab.
    SEAD - The Strategic Environmental Archaeology Database: Progress Report Spring 20142014Report (Other academic)
    Abstract [en]

    This report provides an overview of the progress and results of the VR:KFI infrastructure projects 2007-7494 and (825-)2010-5976. It should be considered as a status report in an on-going long-term research infrastructure development project.

  • 236.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Eriksson, Erik
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Linderholm, Johan
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Viklund, Karin
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Engelmark, Roger
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Palm, Fredrik
    Umeå University, Faculty of Arts, Humlab.
    Svensson, Patrik
    Umeå University, Faculty of Arts, Humlab.
    Buckland, Paul
    Panagiotakopulu, Eva
    Institute of Geography, School of GeoSciences, University of Edinburgh, UK.
    Olofsson, Johan
    Uppsala Municipal Council, Uppsala, Sweden.
    Integrating human dimensions of Arctic palaeoenvironmental science: SEAD – the strategic environmental archaeology database2011In: Journal of Archaeological Science, ISSN 0305-4403, E-ISSN 1095-9238, Vol. 38, no 2, p. 345-351Article in journal (Refereed)
    Abstract [en]

    Environmental change has a human dimension, and has had so for at least the last 10 000 years. The prehistoric impact of people on the Arctic landscape has occasionally left visible traces, such as house and field structures. More often than not, however, the only evidence available is at the microscopic or geochemical level, such as fossil insect and seed assemblages or changes in the physical and chemical properties of soils and sediments. These records are the subject of SEAD, a multidisciplinary database and software project currently underway at Umeå University, Sweden, which aims to create an online database and set of tools for investigating these traces, as part of an international research infrastructure for palaeoecology and environmental archaeology.

  • 237.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Hammarlund, Dan
    Lund University.
    Hjärthner-Holdar, Eva
    Swedish National Historical Museums.
    Lidén, Kerstin
    Stockholm University.
    Lindahl, Anders
    Lund University.
    Palm, Fredrik
    Umeå University, Faculty of Arts, Humlab.
    Possnert, Göran
    Uppsala University.
    The Strategic Environmental Archaeology Database: a resource for international, multiproxy and transdisciplinary studies of environmental and climatic change2015Conference paper (Refereed)
    Abstract [en]

    Climate and environmental change are global challenges which require global data and infrastructure to investigate. These challenges also require a multi-proxy approach, integrating evidence from Quaternary science and archaeology with information from studies on modern ecology and physical processes among other disciplines. The Strategic Environmental Archaeology Database (SEAD http://www.sead.se) is a Swedish based international research e-infrastructure for storing, managing, analysing and disseminating palaeoenvironmental data from an almost unlimited number of analysis methods. The system currently makes available raw data from over 1500 sites (>5300 datasets) and the analysis of Quaternary fossil insects, plant macrofossils, pollen, geochemistry and sediment physical properties, dendrochronology and wood anatomy, ceramic geochemistry and bones, along with numerous dating methods. This capacity will be expanded in the near future to include isotopes, multi-spectral and archaeo-metalurgical data. SEAD also includes expandable climate and environment calibration datasets, a complete bibliography and extensive metadata and services for linking these data to other resources. All data is available as Open Access through http://qsead.sead.se and downloadable software.

     

    SEAD is maintained and managed at the Environmental Archaeology Lab and HUMlab at Umea University, Sweden. Development and data ingestion is progressing in cooperation with The Laboratory for Ceramic Research and the National Laboratory for Wood Anatomy and Dendrochronology at Lund University, Sweden, the Archaeological Research Laboratory, Stockholm University, the Geoarchaeological Laboratory, Swedish National Historical Museums Agency and several international partners and research projects. Current plans include expanding its capacity to serve as a data source for any system and integration with the Swedish National Heritage Board's information systems.

     

    SEAD is partnered with the Neotoma palaeoecology database (http://www.neotomadb.org) and a new initiative for building cyberinfrastructure for transdisciplinary research and visualization of the long-term human ecodynamics of the North Atlantic funded by the National Science Foundation (NSF).

  • 238.
    Buckland, Philip I
    et al.
    Umeå University, Faculty of Arts, Archaeology and Sami Studies.
    Johan, Olofsson
    Umeå University, Faculty of Arts, Archaeology and Sami Studies.
    Engelmark, Roger
    Umeå University, Faculty of Arts, Archaeology and Sami Studies.
    SEAD: Strategic Environmental Archaeology Database, planning report2006Report (Other academic)
    Abstract [en]

    This document lays out a strategy for the development of SEAD – A Strategic Environmental Archaeology Database, which will facilitate the digitisation and accessibility augmentation of MAL’s existing data from nearly thirty years of work in the fields of archaeology and environmental science. SEAD will also provide a framework for the entry of data from all future research and consultancy work at MAL, and allow guest researchers and external partners to contribute to, and work with the same data. The planned system will be implemented at both local and internet levels, and be designed with an aim towards broadening its scope with external partners in the future. SEAD will be made available online in order to increase the ease of access to environmental archaeology data and encourage an expansion of both the discipline and Sweden’s role in it. This is inline with current EU strategies on enhancing research infrastructure, and providing a greater insight into human-environment interactions for long term planning.

  • 239.
    Buckland, Philip I.
    et al.
    Department of Archaeology and Prehistory, University of Sheffield, Sheffield, UK.
    Sadler, Jon
    Manual for the Beta test version of BUGS: a computer based palaeoentomological research aid1995Report (Other academic)
  • 240.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Sjölander, Mattias
    Blombocken avslöjar forntiden: Databaser.2017In: Populär arkeologi, ISSN 0281-014, no 5, p. 28-31Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Databaser. Fossila insekter och förkolnade fröer kan ge mycket information om de miljöer som människor har levt i och kan liksom annan biologisk information tjäna arkeologi

  • 241.
    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.

  • 242. Burman, Erik
    et al.
    Hansbo, Peter
    Larson, Mats G.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    A simple finite element method for elliptic bulk problems with embedded surfaces2019In: Computational Geosciences, ISSN 1420-0597, E-ISSN 1573-1499, Vol. 23, no 1, p. 189-199Article in journal (Refereed)
    Abstract [en]

    In this paper, we develop a simple finite element method for simulation of embedded layers of high permeability in a matrix of lower permeability using a basic model of Darcy flow in embedded cracks. The cracks are allowed to cut through the mesh in arbitrary fashion and we take the flow in the crack into account by superposition. The fact that we use continuous elements leads to suboptimal convergence due to the loss of regularity across the crack. We therefore refine the mesh in the vicinity of the crack in order to recover optimal order convergence in terms of the global mesh parameter. The proper degree of refinement is determined based on an a priori error estimate and can thus be performed before the actual finite element computation is started. Numerical examples showing this effect and confirming the theoretical results are provided. The approach is easy to implement and beneficial for rapid assessment of the effect of crack orientation and may for example be used in an optimization loop.

  • 243. Burman, Erik
    et al.
    Hansbo, Peter
    Larson, Mats G.
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Samvin, David
    A cut finite element method for elliptic bulk problems with embedded surfaces2019In: GEM - International Journal on Geomathematics, ISSN 1869-2672, E-ISSN 1869-2680, Vol. 10, no 1, article id UNSP 10Article in journal (Refereed)
    Abstract [en]

    We propose an unfitted finite element method for flow in fractured porous media. The coupling across the fracture uses a Nitsche type mortaring, allowing for an accurate representation of the jump in the normal component of the gradient of the discrete solution across the fracture. The flow field in the fracture is modelled simultaneously, using the average of traces of the bulk variables on the fractures. In particular the Laplace-Beltrami operator for the transport in the fracture is included using the average of the projection on the tangential plane of the fracture of the trace of the bulk gradient. Optimal order error estimates are proven under suitable regularity assumptions on the domain geometry. The extension to the case of bifurcating fractures is discussed. Finally the theory is illustrated by a series of numerical examples.

  • 244.
    Burström, Markus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Zingmark, Mikael
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    How to provide a user friendly search interface based upon a libraries Open Public Access Catalogue2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today many libraries offer their services via Internet and reach billions of visitors in different ages. The problem is that most of these library web sites are not customized for the users and they don’t deliver a good user experience. In this thesis we have studied both the interface and the users of an Open Public Access Catalog called CS Library. We found out how the users use the current system and how they want to use it. To achieve this we gathered data with different user studies at the Ume°a city library. A new interface was developed from the outcome of our user study. We created a set of guidelines that were followed when a new user customized design was developed for CS Library. The new design offers a better user experience and is customized by the users needs, desires and thoughts. The new design has been implemented as an interactive prototype with HTML, CSS, Javascript and Actionscript to convey a better feeling of the interface.

  • 245.
    Byrne, James
    et al.
    Dublin City University, Ireland.
    Svorobej, Sergej
    Dublin City University, Ireland.
    Giannoutakis, Konstantinos M.
    Centre for Research and Technology Hellas, Greece.
    Tzovaras, Dimitrios
    Centre for Research and Technology Hellas, Greece.
    Byrne, P. J.
    Dublin City University, Ireland.
    Östberg, Per-Olov
    Umeå University, Faculty of Science and Technology, Department of Computing Science. Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Gourinovitch, Anna
    Dublin City University, Ireland.
    Lynn, Theo
    Dublin City University, Ireland.
    A review of cloud computing simulation platforms and related environments2017In: Proceedings of the 7th International Conference on Cloud Computing and Services Science: Volume 1: CLOSER, 2017, Vol. 1, p. 679-691Conference paper (Refereed)
    Abstract [en]

    Recent years have seen an increasing trend towards the development of Discrete Event Simulation (DES) platforms to support cloud computing related decision making and research. The complexity of cloud environments is increasing with scale and heterogeneity posing a challenge for the efficient management of cloud applications and data centre resources. The increasing ubiquity of social media, mobile and cloud computing combined with the Internet of Things and emerging paradigms such as Edge and Fog Computing is exacerbating this complexity. Given the scale, complexity and commercial sensitivity of hyperscale computing environments, the opportunity for experimentation is limited and requires substantial investment of resources both in terms of time and effort. DES provides a low risk technique for providing decision support for complex hyperscale computing scenarios. In recent years, there has been a significant increase in the development and extension of tools to support DES for cloud computing resulting in a wide range of tools which vary in terms of their utility and features. Through a review and analysis of available literature, this paper provides an overview and multi-level feature analysis of 33 DES tools for cloud computing environments. This review updates and extends existing reviews to include not only autonomous simulation platforms, but also on plugins and extensions for specific cloud computing use cases. This review identifies the emergence of CloudSim as a de facto base platform for simulation research and shows a lack of tool support for distributed execution (parallel execution on distributed memory systems).

  • 246.
    Bäckman, Nils
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Collision Detection of TriangleMeshes using GPU2011Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Collision detection in physics engines often use primitives such as spheres and boxes since collisions between these objects are straightforward to compute. More complicated objects can then be modeled using compounds of these simpler primitives. However, in the pursuit of making it easier to construct and simulate complicated objects, triangle meshes are a good alternative since it is usually the format used by modeling tools. This thesis demonstrates how triangle meshes can be used directly as collision objects within a physics engine. The collision detection is done using triangle mesh models with tests accelerated using a tree-based bounding volume hierarchy structure. OpenCL is a new open industry framework for writing programs on heterogeneous platforms, including highly parallel platforms such as Graphics Processing Units(GPUs). Through the use of OpenCL, parallelization of triangle mesh collision detection is implemented for the GPU, then evaluated and compared to the CPU implementation

  • 247.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Bundle adjustment with and without damping2013In: Photogrammetric Record, ISSN 0031-868X, E-ISSN 1477-9730, Vol. 28, no 144, p. 396-415Article in journal (Refereed)
    Abstract [en]

    The least squares adjustment (LSA) method is studied as an optimisation problem and shown to be equivalent to the undamped Gauss-Newton (GN) optimisation method. Three problem-independent damping modifications of the GN method are presented: the line-search method of Armijo (GNA); the Levenberg-Marquardt algorithm (LM); and Levenberg-Marquardt-Powell (LMP). Furthermore, an additional problem-specific "veto" damping technique, based on the chirality condition, is suggested. In a perturbation study on a terrestrial bundle adjustment problem the GNA and LMP methods with veto damping can increase the size of the pull-in region compared to the undamped method; the LM method showed less improvement. The results suggest that damped methods can, in many cases, provide a solution where undamped methods fail and should be available in any LSA software package. Matlab code for the algorithms discussed is available from the authors.

  • 248.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Camera Calibration using the Damped Bundle Adjustment Toolbox2014In: ISPRS Annals - Volume II-5, 2014: ISPRS Technical Commission V Symposium 23–25 June 2014, Riva del Garda, Italy / [ed] F. Remondino and F. Menna, Copernicus GmbH , 2014, Vol. II-5, p. 89-96Conference paper (Refereed)
    Abstract [en]

    Camera calibration is one of the fundamental photogrammetric tasks. The standard procedure is to apply an iterative adjustment to measurements of known control points. The iterative adjustment needs initial values of internal and external parameters. In this paper we investigate a procedure where only one parameter - the focal length is given a specific initial value. The procedure is validated using the freely available Damped Bundle Adjustment Toolbox on five calibration data sets using varying narrow- and wide-angle lenses. The results show that the Gauss-Newton-Armijo and Levenberg-Marquardt-Powell bundle adjustment methods implemented in the toolbox converge even if the initial values of the focal length are between 1/2 and 32 times the true focal length, even if the parameters are highly correlated. Standard statistical analysis methods in the toolbox enable manual selection of the lens distortion parameters to estimate, something not available in other camera calibration toolboxes. A standardised camera calibration procedure that does not require any information about the camera sensor or focal length is suggested based on the convergence results. The toolbox source and data sets used in this paper are available from the authors.

  • 249.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    Experiments with Metadata-derived Initial Values and Linesearch Bundle Adjustment in Architectural Photogrammetry2013Conference paper (Refereed)
    Abstract [en]

    According to the Waldhäusl and Ogleby (1994) "3x3 rules", a well-designed close-range architetural photogrammetric project should include a sketch of the project site with the approximate position and viewing direction of each image. This orientation metadata is important to determine which part of the object each image covers. In principle, the metadata could be used as initial values for the camera external orientation (EO) parameters. However, this has rarely been used, partly due to convergence problem for the bundle adjustment procedure.

    In this paper we present a photogrammetric reconstruction pipeline based on classical methods and investigate if and how the linesearch bundle algorithms of Börlin et al. (2004) and/or metadata can be used to aid the reconstruction process in architectural photogrammetry when the classical methods fail. The primary initial values for the bundle are calculated by the five-point algorithm by Nistér (Stewénius et al., 2006). Should the bundle fail, initial values derived from metadata are calculated and used for a second bundle attempt.

    The pipeline was evaluated on an image set of the INSA building in Strasbourg. The data set includes mixed convex and non-convex subnetworks and a combination of manual and automatic measurements.

    The results show that, in general, the classical bundle algorithm with five-point initial values worked well. However, in cases where it did fail, linesearch bundle and/or metadata initial values did help. The presented approach is interesting for solving EO problems when the automatic orientation processes fail as well as to simplify keeping a link between the metadata containing the plan of how the project should have become and the actual reconstructed network as it turned out to be.

  • 250.
    Börlin, Niclas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Grussenmeyer, Pierre
    INSA Strasbourg, France.
    External Verification of the Bundle Adjustment in Photogrammetric Software Using the Damped Bundle Adjustment Toolbox2016In: XXIII ISPRS Congress, Commission V: Volume XLI-B5 / [ed] L. Halounova, V. Šafář, F. Remondino, J. Hodač, K. Pavelka, M. Shortis, F. Rinaudo, M. Scaioni, J. Boehm, and D. Rieke-Zapp, International Society of Photogrammetry and Remote Sensing , 2016, Vol. XLI-B5, p. 7-14Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to investigate whether the Matlab-based Damped Bundle Adjustment Toolbox (DBAT) can be used to provide independent verification of the BA computation of two popular software—PhotoModeler (PM) and PhotoScan (PS).

    For frame camera data sets with lens distortion, DBAT is able to reprocess and replicate subsets of PM results with high accuracy. For lens-distortion-free data sets, DBAT can furthermore provide comparative results between PM and PS. Data sets for the discussed projects are available from the authors.

    The use of an external verification tool such as DBAT will enable users to get an independent verification of the computations of their software. In addition, DBAT can provide computation of quality parameters such as estimated standard deviations, correlation between parameters, etc., something that should be part of best practice for any photogrammetric software. Finally, as the code is free and open-source, users can add computations of their own.

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