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  • 401.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Bensch, Suna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Understandable Robots: What, Why, and How2018Inngår i: Paladyn - Journal of Behavioral Robotics, ISSN 2080-9778, E-ISSN 2081-4836, Vol. 9, nr 1, s. 110-123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As robots become more and more capable and autonomous, there is an increasing need for humans to understand what the robots do and think. In this paper, we investigate what such understanding means and in- cludes, and how robots can be designed to support un- derstanding. After an in-depth survey of related earlier work, we discuss examples showing that understanding includes not only the intentions of the robot, but also de- sires, knowledge, beliefs, emotions, perceptions, capabil- ities, and limitations of the robot. The term understandingis formally defined, and the term communicative actions is defined to denote the various ways in which a robot may support a human’s understanding of the robot. A novel model of interaction for understanding is presented. The model describes how both human and robot may utilize a first or higher-order theory of mind to understand each other and perform communicative actions in order to sup- port the other’s understanding. It also describes simpler cases in which the robot performs static communicative actions in order to support the human’s understanding of the robot. In general, communicative actions performed by the robot aim at reducing the mismatch between the mind of the robot, and the robot’s inferred model of the human’s model of the mind of the robot. Based on the pro- posed model, a set of questions are formulated, to serve as support when developing and implementing the model in real interacting robots.

  • 402.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Hohnloser, Peter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Tree diameter estimation using laser scanner2012Rapport (Annet vitenskapelig)
    Abstract [en]

    Accurate vehicle localization in forest environments is still an unresolved problem. GPS has obvious limitations in dense forest, and has to be mixed with other techniques to provide satisfying solutions. One possible way is to localize the vehicle relative to trees detected around the vehicle. The first step to implement this method is is to find reliable methods to detect trees, and also to match them to maps. The reliability of this matching operation is improved by accurate estimations of tree diameter. In this paper we evaluate a number of existing algorithms for detection of trees and estimation of tree diameter. Three new algorithms are also suggested. All algorithms were evaluated in field experiments at three different locations with varying tree trunk visibility. The results show that one of the existing algorithms is clearly less reliable than the other two. Noticeable is that the existing algorithms often overestimate tree trunk diameter. The new algorithms mostly underestimate, but are most accurate in some situations. 

  • 403.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Johansson, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A Java-based middleware for control and sensing in mobile robotics2008Inngår i: International Conference on Intelligent Automation and Robotics 2008, 2008, s. 649-654Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Many of the existing mobile-robot software packages do not include handling of sensors and actuators in a sufficiently systematic and uniform way, as described later in this section. The software framework proposed in this paper, denoted NAV2000, addresses the specific need for interchangeability of components in robotics. At the lowest level, sensors, and sometimes also actuators, often have to be replaced by similar, yet not identical, components. At a higher level, the target vehicle often changes during the work process. The presented software provides a framework that supports these replacements and allows configurations of sensors, actuators, and target machines to be specified and manipulated in an efficient manner. The system can be distributed over a network of computers if some software modules require more computing power, i.e. more hardware can be added to the system without any software changes. To accomplish sufficient monitoring of the system's health, a dedicated system keeps track of all software modules. The system uses logfiles to enable convenient debugging and performance analysis of hardware and software modules. The software has been developed as part of, and is currently in use in, a R&D-project for an autonomous path-tracking forest machine.

  • 404.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Johansson, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    A Software Framework for Control and Sensing in Mobile Robotics2007Rapport (Annet vitenskapelig)
    Abstract [en]

    Many of the existing mobile-robot softwares do not include handling of sensors and actuators in a sufficiently systematic and uniform way. The software framework proposed in this paper addresses the specific need for interchangeability of components in robotics. At the lowest level, sensors, and sometimes also actuators, often have to be replaced by similar, yet not identical, components. At a higher level, the target vehicle for the developed system often changes during the work process. The presented software provides a framework that supports these replacements and allows configurations of sensors, actuators, and target machines to be specified and manipulated in an efficient manner. The system can be run on several different computers if some software modules require more computing power. To accomplish sufficient monitoring of the system's health, a dedicated system keeps track of all software modules loaded onto the local computer, and also communicates with health monitors in all other computers running the system. The overall health of every module as well as a more detailed description of possible problems is presented graphically. In addition to this, the system uses logfiles to enable convenient debugging and performance analysis of hardware and software modules. The software has been developed as part of, and is currently in use in, a R&D-project for an autonomous path-tracking forest machine.

  • 405.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Johansson, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Development of an Autonomous Forest Machine for Path Tracking2006Inngår i: Field and Service Robotics: Results of the 5th International Conference, New York: Springer , 2006, s. 603-614Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In many respects traditional automation in the forest-machine industry hasreached an upper limit, since the driver already has to deal with an excess ofinformation and take too many decisions at a very high pace. To furtherautomation still, introduction of semi-autonomous and autonomous functions areexpected and considered necessary. This paper describes an ongoing projectalong these ideas. We describe the development of the hardware and software ofan unmanned shuttle that shifts timber from the area of felling to the mainroads for further transportation. A new path-tracking algorithm is introduced,and demonstrated as being superior to standard techniques, such as Follow theCarrot and Pure Pursuit. To facilitate the research and development, acomprehensive software architecture for sensor and actuator interfacing isdeveloped. Obstacle avoidance is accomplished by a new kind of radar,developed for and by the automotive industry. Localization is accomplished by combining data from a Real-Time Kinematic DifferentialGPS/GLONASS and odometry. Tests conducted on a simulator and asmall-scale robot show promising results. Tests on the real forest machine areongoing.

  • 406.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lärkeryd, Per
    Indexator .
    Nordfjell, Tomas
    Department of Forest Resource Management, Swedish University of Agricultural Sciences.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Autonomous forest vehicles: historic, envisioned, and state-of-the-art2009Inngår i: International Journal of Forest Engineering, ISSN 1494-2119, E-ISSN 1913-2220, Vol. 20, nr 1, s. 33-38Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The feasibility of using autonomous forest vehicles (which can be regarded as logical developments in the ongoing automation of forest machines), the systems that could be applied in them, their potential advantages and their limitations (in the foreseeable future) are considered here. The aims were to analyse: (1) the factors influencing the degree of automation in logging; (2) the technical principles that can be applied to autonomous forest machines, and (3) the feasibility of developing an autonomous path-tracking forest vehicle. A type of vehicle that is believed to have considerable commercial potential is an autonomous forwarder. The degree of automation is influenced by increased productivity, the machine operator as a bottle-neck, cost reduction, and environmental aspects. Technical principles that can be applied to autonomous forest vehicles are satellite navigation, wheel odometry, laser scanner and radar. A new path-tracking algorithm has been developed to reduce deviations from the desired path by utilizing the driver’s steering commands. The presented system has demonstrated both possibilities and difficulties associated with autonomous forest machines. It is in a field study shown that it is quite possible for them to learn and track a path previously demonstrated by an operator with an accuracy of 0.1m on flat ground and also to detect and avoid unexpected obstacles. Although the forest machine safely avoids obstacles, the study shows that further research in the field of obstacle avoidance is needed to optimize performance and ensure safe operation in a real forest environment.

  • 407.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A simulator driven path planner for autonomous off-road vehicles – initial results2008Inngår i: Proceedings of the Israel Conference on Robotics (ICR08), 2008Konferansepaper (Fagfellevurdert)
  • 408.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Follow the Past: a Path Tracking Algorithm for Autonomous Vehicles2006Inngår i: International Journal of Vehicle Autonomous Systems, ISSN 1741-5306, Vol. 4, nr 2/3/4, s. 216-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A number of algorithms for path tracking are described in the robotics literature. Traditional algorithms, like Pure Pursuit and Follow the Carrot, use position information to compute steering commands that make a vehicle follow a pre-defined path approximately. These algorithms are well known to cut corners, since they do not explicitly take into account the actual curvature of the path. In this paper we present a novel algorithm that uses recorded steering commands to overcome this problem. The algorithm is constructed within the behavioural paradigm common in intelligent robotics and is divided into three separate behaviours, each responsible for one aspect of the path-tracking task. The algorithm is implemented both on a simulator for autonomous forest machines and a physical small-scale robot. The results are compared with the Pure Pursuit and the Follow the Carrot algorithms and show a significant improvement in performance.

  • 409.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Path planning for off-road vehicles with a simulator-in-the-loop2008Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper describes the development of a real-time path planner for off-road vehicles using a simulator. The work was triggered by a need for an obstacle-avoidance and path-planning system in our work with autonomous forest machines. The general idea with the presented system is to extend a standard path-tracking algorithm with a simulator that, in real-time, tries to predict collisions in a window forward in time. This simulation is based on current sensor data giving information about the environment around the vehicle. If a collision is predicted, the vehicle is stopped and a path-search phase is initiated. Variants of the original path are generated and simulated until a feasible path is found. The real vehicle then continues, now tracking the replanned path. In simulated tests, this way of using a simulator to predict and avoid collisions works well. The system is able to safely navigate around obstacles on and close to the path in a way that is hard or impossible to achieve with standard obstacle-avoidance algorithms that do not take the shape of the vehicle into account. Another scenario, also envisioned in forest environment, is off-line path planning of a longer route, based on map information. An approximate path given by a straight line from start to goal is then modified in the same way as described above.

  • 410.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ringdahl, Ola
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Real-time path planning using a simulator-in-the-loop2009Inngår i: International Journal Vehicle Autonomous Systems, ISSN 1471-0226, Vol. 7, nr 1/2, s. 56-72Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper describes the development of a real-time path planner for off-road vehicles using a simulator. The general idea with the presented system is to extend a standard path-tracking algorithm with a simulator that, in real-time, tries to predict collisions in a window forward in time. If a collision is predicted, the vehicle is stopped and a path-search phase is initiated. Variants of the original path are generated and simulated until a feasible path is found. The real vehicle then continues, now tracking the replanned path.

  • 411.
    Hellström, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Ringdahl, Ola
    Johansson, ThomasA java-based middleware for control and sensing in mobile robotics
    A java-based middleware for control and sensing in mobile robotics2008Inngår i: Proceedings of the International Conference on Intelligent Automation and Robotics 2008 (ICIAR’08), 2008, s. 649-654Konferansepaper (Fagfellevurdert)
  • 412.
    Holme, Petter
    Dept. of Energy Science,Sungkyunkwan University,Suwon 440-746,Korea.
    Model versions and fast algorithms for network epidemiology2014Inngår i: Journal of Logistical Engineering University, ISSN 1672-7843, Vol. 30, nr 3, s. 1-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Network epidemiology has become a core framework for investigating the role of human contact patterns in the spreading of infectious diseases. In network epidemiology, one represents the contact structure as a network of nodes (individuals) connected by links (sometimes as a temporal network where the links are not continuously active) and the disease as a compartmental model (where individuals are assigned states with respect to the disease and follow certain transition rules between the states). In this paper, we discuss fast algorithms for such simulations and also compare two commonly used versions,one where there is a constant recovery rate (the number of individuals that stop being infectious per time is proportional to the number of such people);the other where the duration of the disease is constant. The results show that, for most practical purposes, these versions are qualitatively the same.

  • 413.
    Holme, Petter
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Huss, Mikael
    Science of Life Laboratory.
    Understanding and Exploiting Information Spreading and Integrating Technologies2011Inngår i: Journal of Computer Science and Technology, ISSN 1000-9000, E-ISSN 1860-4749, Vol. 26, nr 5, s. 829-836Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Our daily life leaves an increasing amount of digital traces, footprints that are improving our lives. Data-mining tools, like recommender systems, convert these traces to information for aiding decisions in an ever-increasing number of areas in our lives. The feedback loop from what we do, to the information this produces, to decisions what to do next, will likely be an increasingly important factor in human behavior on all levels from individuals to societies. In this essay, we review some effects of this feedback and discuss how to understand and exploit them beyond mapping them on more well-understood phenomena. We take examples from models of spreading phenomena in social media to argue that analogies can be deceptive, instead we need to fresh approaches to the new types of data, something we exemplify with promising applications in medicine.

  • 414.
    Holmström, Adam
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Performance and Usability Improvements for Massive Data Grids using Silverlight2011Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    TRIMMA Affärsutveckling AB is developing and marketing a business intelligence solution called INSIGHT. INSIGHT presents tables showing possibly very large data sets and the performance and user experience is sometimes suffering. The main objective of this thesis is an evaluation of the pros and cons of replacing the existing ASP.NET/HTML table component in INSIGHT with a component developed in Silverlight.This thesis examines two techniques to speed up a Silverlight application showing a lot of data: UI- and data virtualization. UI virtualization intends to render only the user interface elements that appear on the screen and are visible to the user, while data virtualization intends to fetch (from the data source) only the section of the data that is visible to the user. The result of the project is a fully working prototype integrated into a test version of INSIGHT. Performance testing results indicate that the prototype performs approximately the same as the ASP.NET/HTML version of INSIGHT for small tables but significantly better for large data sets. 

    The prototype also contains a few extra features, not available in INSIGHT, exemplifying the possibilities to create highly responsive user interfaces in Silverlight

  • 415. Huang, Xiao-Yu
    et al.
    Li, Wubin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Chen, Kang
    Xiang, Xian-Hong
    Pan, Rong
    Li, Lei
    Cai, Wen-Xue
    Multi-Matrices Factorization with Application to Missing Sensor Data Imputation2013Inngår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 13, nr 11, s. 15172-15186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We formulate a multi-matrices factorization model (MMF) for the missing sensor data estimation problem. The estimation problem is adequately transformed into a matrix completion one. With MMF, an n-by-t real matrix, R, is adopted to represent the data collected by mobile sensors from n areas at the time, T-1, T-2, . . . , T-t, where the entry, R-i,R-j, is the aggregate value of the data collected in the ith area at T-j. We propose to approximate R by seeking a family of d-by-n probabilistic spatial feature matrices, U-(1), U-(2), . . . , U-(t), and a probabilistic temporal feature matrix, V epsilon R-dxt, where R-j approximate to U-(j)(T) T-j. We also present a solution algorithm to the proposed model. We evaluate MMF with synthetic data and a real-world sensor dataset extensively. Experimental results demonstrate that our approach outperforms the state-of-the-art comparison algorithms.

  • 416.
    Hägg, Linus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Quasi-Arithmetic Filters for Topology Optimization2016Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Topology optimization is a framework for finding the optimal layout of material within a given region of space. In material distribution topology optimization, a material indicator function determines the material state at each point within the design domain. It is well known that naive formulations of continuous material distribution topology optimization problems often lack solutions. To obtain numerical solutions, the continuous problem is approximated by a finite-dimensional problem. The finite-dimensional approximation is typically obtained by partitioning the design domain into a finite number of elements and assigning to each element a design variable that determines the material state of that element. Although the finite-dimensional problem generally is solvable, a sequence of solutions corresponding to ever finer partitions of the design domain may not converge; that is, the optimized designs may exhibit mesh-dependence. Filtering procedures are amongst the most popular methods used to handle the existence issue related to the continuous problem as well as the mesh-dependence related to the finite-dimensional approximation. Over the years, a variety of filters for topology optimization have been presented.

    To harmonize the use and analysis of filters within the field of topology optimization, we introduce the class of fW-mean filters that is based on the weighted quasi-arithmetic mean, also known as the weighted generalized f-mean, over some neighborhoods. We also define the class of generalized fW-mean filters that contains the vast majority of filters for topology optimization. In particular, the class of generalized fW-mean filters includes the fW-mean filters, as well as the projected fW-mean filters that are formed by adding a projection step to the fW-mean filters.

    If the design variables are located in a regular grid, uniform weights are used within each neighborhood, and equal sized polytope shaped neighborhoods are used, then a cascade of generalized fW-mean filters can be applied with a computational complexity that is linear in the number of design variables. Detailed algorithms for octagonal shaped neighborhoods in 2D and rhombicuboctahedron shaped neighborhoods in 3D are provided. The theoretically obtained computational complexity of the algorithm for octagonal shaped neighborhoods in 2D has been numerically verified. By using the same type of algorithm as for filtering, the additional computational complexity for computing derivatives needed in gradient based optimization is also linear in the number of design variables.

    To exemplify the use of generalized fW-mean filters in topology optimization, we consider minimization of compliance (maximization of global stiffness) of linearly elastic continuum bodies. We establish the existence of solutions to a version of the continuous minimal compliance problem when a cascade of projected continuous fW-mean filters is included in the formulation. Bourdin's classical existence result for the linear density filter is a partial case of this general theorem for projected continuous fW-mean filters. Inspired by the works of Svanberg & Svärd and Sigmund, we introduce the harmonic open-close filter, which is a cascade of four fW-mean filters. We present large-scale numerical experiments indicating that, for minimal compliance problems, the harmonic open-close filter produces almost binary designs, provides independent size control on both material and void regions, and yields mesh-independent designs.

  • 417.
    Hägg, Linus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Wadbro, Eddie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Nonlinear filters in topology optimization: existence of solutions and efficient implementation for minimal compliance problems2016Rapport (Annet vitenskapelig)
    Abstract [en]

    It is well known that material distribution topology optimization problems often are ill-posed if no restriction or regularization method is used. A drawback with the standard linear density filter is that the resulting designs have large areas of intermediate densities, so-called gray areas, especially when large filter radii are used. To produce final designs with less gray areas, several different methods have been proposed; for example, projecting the densities after the filtering or using a nonlinear filtering procedure. In a recent paper, we presented a framework that encompasses a vast majority of currently available density filters. In this paper, we show that all these nonlinear filters ensure existence of solutions to a continuous version of the minimal compliance problem. In addition, we provide a detailed description on how to efficiently compute sensitivities for the case when multiple of these nonlinear filters are applied in sequence. Finally, we present a numerical experiment that illustrates that these cascaded nonlinear filters can be used to obtain independent size control of both void and material regions in a large-scale setting.

  • 418.
    Hägg, Linus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Wadbro, Eddie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    On minimum length scale control in density based topology optimization2018Inngår i: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 58, nr 3, s. 1015-1032Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The archetypical topology optimization problem concerns designing the layout of material within a given region of space so that some performance measure is extremized. To improve manufacturability and reduce manufacturing costs, restrictions on the possible layouts may be imposed. Among such restrictions, constraining the minimum length scales of different regions of the design has a significant place. Within the density filter based topology optimization framework the most commonly used definition is that a region has a minimum length scale not less than D if any point within that region lies within a sphere with diameter D > 0 that is completely contained in the region. In this paper, we propose a variant of this minimum length scale definition for subsets of a convex (possibly bounded) domain We show that sets with positive minimum length scale are characterized as being morphologically open. As a corollary, we find that sets where both the interior and the exterior have positive minimum length scales are characterized as being simultaneously morphologically open and (essentially) morphologically closed. For binary designs in the discretized setting, the latter translates to that the opening of the design should equal the closing of the design. To demonstrate the capability of the developed theory, we devise a method that heuristically promotes designs that are binary and have positive minimum length scales (possibly measured in different norms) on both phases for minimum compliance problems. The obtained designs are almost binary and possess minimum length scales on both phases.

  • 419.
    Häggkvist, Roland
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Johansson, Anders
    Orthogonal latin rectangles2008Inngår i: Combinatorics, probability & computing, ISSN 0963-5483, E-ISSN 1469-2163, Vol. 17, nr 4, s. 519-536Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use a greedy probabilistic method to prove that, for every epsilon > 0, every m x n Latin rectangle on n symbols has an orthogonal mate, where m = (1 - epsilon)n. That is, we show the existence of a second Latin rectangle such that no pair of the mn cells receives the same pair of symbols in the two rectangles.

  • 420.
    Högberg, Johanna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    An inference algorithm for regular tree languages2011Inngår i: Natural Language Engineering, ISSN 1351-3249, E-ISSN 1469-8110, Vol. 17, nr 2, s. 203-219Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a randomized inference algorithm for regular tree languages. The algorithm takes as input two disjoint finite nonempty sets of trees P and N, and outputs a nondeterministic finite tree automaton that accepts every tree in P, and rejects every tree in N. The output automaton typically represents a non-trivial generalisation of the examples given in P and N. To obtain compact output automata, we use a heuristics similar to bisimulation minimization.The algorithm has time complexity of O(|N||P|^2). Experiments are conducted on a prototype implementation, and the empirical results appear to second the theoretical results.

  • 421.
    Högberg, Johanna
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Contributions to the theory and applications of tree languages2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis is concerned with theoretical as well as practical aspects of tree languages. It consists of an introduction and eight papers, organised into three parts. The first part is devoted to algorithmic learning of regular tree languages, the second part to bisimulation minimisation of tree automata, and the third part to tree-based generation of music. We now summarise the contributions made in each part.

    In Part I, an inference algorithm for regular tree languages is presented. The algorithm is a generalisation of a previous algorithm by Angluin, and the learning task is to derive, with the aid of a so-called MAT-oracle, the minimal (partial and deterministic) finite tree automaton M that recognises the target language U over some ranked alphabet Σ. The algorithm executes in time O(|Q| |δ| (m + |Q|)), where Q and δ are the set of states and the transition table of M , respectively, r is the maximal rank of any symbol in Σ, and m is the maximum size of any answer given by the oracle. This improves on a similar algorithm by Sakakibara as dead states are avoided both in the learning phase and in the resulting automaton. Part I also describes a concrete implementation which includes two extensions of the basic algorithm.

    In Part II, bisimulation minimisation of nondeterministic weighted tree automata (henceforth, wta) is introduced in general, and for finite tree automata (which can be seen as wta over the Boolean semiring) in particular. The concepts of backward and forward bisimulation are extended to wta, and efficient minimisation algorithms are developed for both types of bisimulation. In the special case where the underlying semiring of the input automaton is either cancellative or Boolean, these minimisation algorithms can be further optimised by adapting existing partition refinement algorithms by Hopcroft, Paige, and Tarjan. The implemented minimisation algorithms are demonstrated on a typical task in natural language processing.

    In Part III, we consider how tree-based generation can be applied to algorithmic composition. An algebra is presented whose operations act on musical pieces, and a system capable of generating simple musical pieces is implemented in the software Treebag: starting from input which is either generated by a regular tree grammar or provided by the user via a digital keyboard, a number of top-down tree transducers are applied to generate a tree over the operations provided by the music algebra. The evaluation of this tree yields the musical piece generated.

  • 422. Höppner, F.
    et al.
    Klawonn, F.
    Eklund, Patrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Learning indistinguishability from data2002Inngår i: Soft Computing - A Fusion of Foundations, Methodologies and Applications, ISSN 1432-7643, E-ISSN 1433-7479, Vol. 6, nr 1, s. 6-13Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we revisit the idea of interpreting fuzzy sets as representations of vague values. In this context a fuzzy set is induced by a crisp value and the membership degree of an element is understood as the similarity degree between this element and the crisp value that determines the fuzzy set. Similarity is assumed to be a notion of distance. This means that fuzzy sets are induced by crisp values and an appropriate distance function. This distance function can be described in terms of scaling the ordinary distance between real numbers. With this interpretation in mind, the task of designing a fuzzy system corresponds to determining suitable crisp values and appropriate scaling functions for the distance. When we want to generate a fuzzy model from data, the parameters have to be fitted to the data. This leads to an optimisation problem that is very similar to the optimisation task to be solved in objective function based clustering. We borrow ideas from the alternating optimisation schemes applied in fuzzy clustering in order to develop a new technique to determine our set of parameters from data, supporting the interpretability of the fuzzy system.

  • 423.
    Ibidunmoye, Olumuyiwa
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Metsch, T.
    Bayon-Molino, V.
    Elmroth, E.
    Performance Anomaly Detection using Datacenter Landscape GraphsManuskript (preprint) (Annet vitenskapelig)
  • 424.
    Ibidunmoye, Olumuyiwa
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Metsch, T.
    Elmroth, E.
    Real-time Detection of Performance Anomalies for Cloud ServiceManuskript (preprint) (Annet vitenskapelig)
  • 425.
    Ikonomidis Svedmark, Eva
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för informatik.
    Med nätet som fält: urvalstankar, känslostormar och etikproblem2011Inngår i: Kulturella perspektiv - Svensk etnologisk tidskrift, ISSN 1102-7908, nr 2, s. 11-21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Writing ethnography involves retelling a story and carrying the voices of others in order to describe and explain a cultural phenomenon. This article argues that the ethnographer cannot write in such a close manner without great difficulties when today's search engines operate with unprecedented vigour. Tracing a text string using Google takes less than a second and this has great implications for the ability to provide quotations if the researcher is to follow ethical guidelines to protect and to keep their informants anonymous. Further, this article discusses ethical implications involved in online studies of blogs where the content is of a sensitive and private nature. To undertake such research while showing respect for the informant is a challenging task, given the researchers need to adhere to the key issues in research ethics. This article specifically problematizes the ethics of informed consent and confidentiality as it provides a particular challenge for the researcher engaged in studies of affective online sharing.

  • 426. Jaasma, Philemonne
    et al.
    Smit, Dorothe
    van Dijk, Jelle
    Latcham, Thomas
    Trotto, Ambra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Arkitekthögskolan vid Umeå universitet. Interactive RI.SE ICT, Umeå, Sweden .
    Hummels, Caroline
    The Blue Studio: Designing an Interactive Environment for Embodied Multi-Stakeholder Ideation Processes2017Inngår i: Proceedings of the Eleventh International Conference on Tangible, Embedded, and Embodied Interaction (TEI'17), New York: Association for Computing Machinery (ACM), 2017, s. 1-10Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper describes the process of designing the Blue Studio: an interactive space for embodied multi-stakeholder ideation processes. Inspired by embodied sensemaking the way people make sense of things through external expression and interaction with other people we iteratively designed material, interactive and spatial interventions in the Blue Studio and evaluated them with multi-stakeholder participants in various studies. Thereupon, we analyzed the impact of the design interventions, based on the seven principles to design for embodied sensemaking and highlighted opportunities for refining our interactive space for embodied ideation. Based on the insights gained, a final design of the Blue Studio was realized and evaluated on functionality.

  • 427.
    Jakobsson, Viktor
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    The Förstner Interest Point Operator Subwindow Localization on SIFT Keypoints2015Independent thesis Advanced level (degree of Master (Two Years)), 300 hpOppgave
    Abstract [en]

    This thesis suggests a modification to the popular Scale Invariant Feature Transform (SIFT) algorithm (Lowe, 2004) often used in photogrammetry and computer vision to find features in images for measurement. The SIFT algorithm works by first detecting points in images at different scales and sizes. It then refines the position of the found points. The algorithm creates a descriptor of the point based on the region around the point. Finally the points can be matched against other points in different images using the descriptor. The suggested modification is built upon a paper by Förstner and Gülch (1987) where a method for performing a subwindow localization is presented. In this thesis the keypoints detected by the SIFT algorithm are modified on the subwindow level in order to improve the robustness with respect to the selected window position. Several different methods of tweaking the suggested modification and the SIFT algorithm were tested. The methods were evaluated on two different test cases. The first used a camera calibration software to compare accuracy of keypoints by looking at the residuals of the calibration. The other test involved creating a point cloud of images of a planar surface, evaluating the results by looking at the standard deviation in keypointoffset from the plane.The results show that neither test gave evidence that the proposed modification was an improvement. It was found that the algorithm had problems with oblique projections of circles, i.e. ellipses. Therefore there is potentialto use homography in special cases to circumvent this problem and get better precision. Furthermore tests involving more lines and intersections in the test images should be performed before this suggested modificationcan be completely discarded.

  • 428. Jankowski, Michal
    et al.
    Elmroth, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Meyer, Norbert
    Authorizing Grid Resource Access and Consumption2009Inngår i: Grid and Services Evolution: Proceedings of the 3rd CoreGRID Workshop on Grid Middleware, Springer-Verlag , 2009, s. 157-168Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The tasks to authorize users access to grid resources and to authorize their regulated consumption is studied and some key functionality is identified. A novel authorization infrastructure is proposed by combining the Virtual User System (VUS) for dynamically assigning local pool-accounts to grid-users and the SweGrid Accounting System (SGAS) for grid-wide usage logging and real-time enforcement of resource pre-allocations.

  • 429.
    Janlert, Lars-Erik
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Available information — preparatory note for a theory of information space2006Inngår i: tripleC, ISSN 1726-670X, Vol. 4, nr 2Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Information technology warps information space, but there are limits to the availability of information. Information distance is introduced to begin investigate the shape of information space, which is very much needed. The concept of availability profile is proposed as a way of defining spatial location in information space, also interpretable as information state. A first check of the possibilities to extend the agentcentric view into an infocentric view is not immediately discouraging, but many problems and issues remain.

  • 430.
    Janlert, Lars-Erik
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Being and Appearing: Human Interfaces in the Digital Age2006Inngår i: Proceedings of 2006 IRMA International Conference: Emerging Trends and Challenges in Information Technology Management, 2006, s. 232-234Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Persons present themselves to the world. The relation between appearance and being is constrained in various ways. The ongoing virtualization disrupts existing mechanisms serving to keep appearance in alignment with being, increases interpretative uncertainty, and threatens to destroy the very distinction; giving us cause to reconsider our notions of identity. 

  • 431.
    Janlert, Lars-Erik
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Dark programming and the case for the rationality of programs2008Inngår i: Journal of Applied Logic, ISSN 1570-8683, E-ISSN 1570-8691, Vol. 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Programming normally proceeds from subjective method to objective method: to program a task, you need to be able to do the task; at least “in principle.” Some new techniques of producing programs, exemplified by evolutionary algorithm techniques, do not involve any such subjective method. Is this still programming, and are the results really programs? To answer, the concept of program is reexamined. It is argued that in addition to being causative and descriptive, a program must also be rationally justifiable, i.e., the specific structure of the program should be explainable by the (rational) ways in which it contributes to achieving the intended goal. Whereas traditional programming is rational in the sense that it provides the program with a rationale by its reliance on subjective method and problem solving, these new techniques of “dark programming” do not produce any rationale; moreover, the results are not restricted to be easily rationalized. Dark programs are not guaranteed to be proper programs, but dark programming can still be used as a tool in proper (rational) programming. The business of programming then takes a turn from problem solving in the sense of invention and engineering towards problem solving in the sense of explanation and research.

  • 432.
    Janlert, Lars-Erik
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Putting pictures in context2006Inngår i: Proceedings of AVI 2006 (ACM), 2006Konferansepaper (Fagfellevurdert)
  • 433.
    Janols, Rebecka
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering.
    Guerrero, Esteban
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindgren, Helena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    A Pilot Study on Personalised Coaching to Increase Older Adults' Physical and Social Activities2017Inngår i: Ambient Intelligence - Software and Applications - 8th International Symposium on Ambient Intelligence (ISAmI 2017) / [ed] Juan F. De Paz, Vicente Julián, Gabriel Villarrubia, Goreti Marreiros, Paulo Novais, Springer, 2017, Vol. 615, s. 140-148Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The aim of this research is to conduct a pilot study of a prototype that provides feedback using theory-based motivating messages developed by older adults, in a context of every day activities that include both physical and social activities. The prototype mobile application integrated the messages, a motivational model, and a personalization module that selects motivational messages based on preferences, motivational profile and the situation. The four participating older adults used the application for planning and following up social and physical activities. They found the messages entertaining and appreciated the dialogues with the application. They used the dialogues primarily to reinforce their satisfaction regarding conducted activities and did not necessarily tell the truth about conduced activities in the interaction with the application. The results are preliminary, but give valuable implications for further development of the personalisation module towards more purposeful use of ambient information, and aspects to explore in future user studies.

  • 434.
    Johansson, Mats
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Eklund, Patrik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Kortelainen, Jari
    South-Eastern Finland University of Applied Sciences, Mikkeli, Finland.
    Winter, Michael
    Brock University, Department of Computer Science, St. Catharines, Ontario, Canada .
    The Algebra, Logic and Topology of System-of-Systems2018Inngår i: Proceedings of the 20th International Dependency and Structure Modeling (DSM) Conference: Trieste (Italy), 15 – 17 October 2018 / [ed] Carlo Leardi, Tyson R. Browning, Steven D. Eppinger, Lucía Becerril, Lehrstuhl für Produktentwicklung und Leichtbau , 2018, Vol. 20, s. 195-202Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we propose an information structure enrichment of relational models underlying design structure models typically used in System-ofSystems. Such design structures are algebraically, logically and topologically mostly unstructured relations as treated within naïve set theory. The paper also aims to show how an enriched information structure can be applied to monitor the health status of a System-of-System as an alternative to fault trees.

  • 435.
    Johansson, Stefan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Reviewing the Closure Hierarchy of Orbits and Bundles of System Pencils and Their Canonical Forms2009Rapport (Annet vitenskapelig)
    Abstract [en]

    Using a unifying terminology and notation an introduction to the theory of stratification for orbits and bundles of matrices, matrix pencils and system pencils with applications in systems and control is presented. Canonical forms of such orbits and bundles reveal the important system characteristics of the models under investigation. A stratification provides the qualitative information of which canonical structures are near each other in the sense of small perturbations. We discuss how fundamental concepts like controllability and observability of a system can be studied with the use of the stratification theory. Important results are presented in the form of the closure and cover relations for controllability and observability pairs. Furthermore, different canonical forms are considered from which we can derive the characteristics of a system. Specifically, we discuss how the Kronecker canonical form is related to the Brunovsky canonical form and its generalizations. Concepts and results are illustrated with several examples throughout the presentation.

  • 436.
    Johansson, Stefan
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Tools for Control System Design: Stratification of Matrix Pairs and Periodic Riccati Differential Equation Solvers2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Modern control theory is today an interdisciplinary area of research. Just as much as this can be problematic, it also provides a rich research environment where practice and theory meet. This Thesis is conducted in the borderline between computing science (numerical analysis) and applied control theory. The design and analysis of a modern control system is a complex problem that requires high qualitative software to accomplish. Ideally, such software should be based on robust methods and numerical stable algorithms that provide quantitative as well as qualitative information.

    The introduction of the Thesis is dedicated to the underlying control theory and to introduce the reader to the main subjects. Throughout the Thesis, the theory is illustrated with several examples, and similarities and differences between the terminology from mathematics, systems and control theory, and numerical linear algebra are highlighted. The main contributions of the Thesis are structured in two parts, dealing with two mainly unrelated subjects.

    Part I is devoted to the qualitative information which is provided by the stratification of orbits and bundles of matrices, matrix pencils and system pencils. Before the theory of stratification is established the reader is introduced to different canonical forms which reveal the system characteristics of the model under investigation. A stratification reveals which canonical structures of matrix (system) pencils are near each other in the sense of small perturbations of the data. Fundamental concepts in systems and control, like controllability and observability of linear continuous-time systems, are considered and it is shown how these system characteristics can be investigated using the stratification theory. New results are presented in the form of the cover relations (nearest neighbours) for controllability and observability pairs. Moreover, the permutation matrices which take a matrix pencil in the Kronecker canonical form to the corresponding system pencil in (generalized) Brunovsky canonical form are derived. Two novel algorithms for determining the permutation matrices are provided.

    Part II deals with numerical methods for solving periodic Riccati differential equations (PRDE:s). The PRDE:s under investigation arise when solving the linear quadratic regulator (LQR) problem for periodic linear time-varying (LTV) systems. These types of (periodic) LQR problems turn up for example in motion planning of underactuated mechanical systems, like a humanoid robot, the Furuta pendulum, and pendulums on carts. The constructions of the nonlinear controllers are based on linear versions found by stabilizing transverse dynamics of the systems along cycles.

    Three different methods explicitly designed for solving the PRDE are evaluated on both artificial systems and stabilizing problems originating from experimental control systems. The methods are the one-shot generator method and two recently proposed methods: the multi-shot method (two variants) and the SDP method. As these methods use different approaches to solve the PRDE, their numerical behavior and performance are dependent on the nature of the underlying control problem. Such method characteristics are investigated and summarized with respect to different user requirements (the need for accuracy and possible restrictions on the solution time).

  • 437.
    Johansson, Stefan
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap.
    Kågström, Bo
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskaplig fakultet, HPC2N (Högpresterande beräkningscentrum norr).
    Shiriaev, Anton
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Varga, Andras
    Institute of Robotics and Mechatronics, German Aerospace Center, DLR, Oberpfaffenhofen, Germany.
    Comparing One-shot and Multi-shot Methods for Solving Periodic Riccati Differential Equations2007Inngår i: Proceedings of the third IFAC Workshop on Periodic Control Systems (PSYCO’07), International Federation of Automatic Control , 2007, s. 1-6Konferansepaper (Fagfellevurdert)
    Abstract [en]

    One-shot methods and recently proposed multi-shot methods for computing stabilizing solutions of continuous-time periodic Riccati differential equations are examined and evaluated on two test problems: (i) a stabilization problem for an artificially constructed time-varying linear system for which the exact solution is known; (ii) a nonlinear stabilization problem for a devil stick juggling model along a periodic trajectory. The numerical comparisons are performed using both general purpose and symplectic integration methods for solving the associated Hamiltonian differential systems. In the multi-shot method a stable subspace is determined using recent algorithms for computing a reordered periodic real Schur form. The results show the increased accuracy achievable by combining multi-shot methods with structure preserving (symplectic) integration techniques.

  • 438.
    Johansson, Stefan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Kågström, Bo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Högpresterande beräkningscentrum norr (HPC2N).
    Van Dooren, Paul
    Department of Mathematical Engineering, Université catholique de Louvain.
    Stratification of full rank polynomial matrices2013Inngår i: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 439, nr 4, s. 1062-1090Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We show that perturbations of polynomial matrices of full normal-rank can be analyzed viathe study of perturbations of companion form linearizations of such polynomial matrices.It is proved that a full normal-rank polynomial matrix has the same structural elements asits right (or left) linearization. Furthermore, the linearized pencil has a special structurethat can be taken into account when studying its stratification. This yields constraintson the set of achievable eigenstructures. We explicitly show which these constraints are.These results allow us to derive necessary and sufficient conditions for cover relationsbetween two orbits or bundles of the linearization of full normal-rank polynomial matrices.The stratification rules are applied to and illustrated on two artificial polynomial matricesand a half-car passive suspension system with four degrees of freedom.

  • 439.
    Jonsson, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Towards semantic language processing2018Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The overall goal of the field of natural language processing is to facilitate the communication between humans and computers, and to help humans with natural language problems such as translation. In this thesis, we focus on semantic language processing. Modelling semantics – the meaning of natural language – requires both a structure to hold the semantic information and a device that can enforce rules on the structure to ensure well-formed semantics while not being too computationally heavy. The devices used in natural language processing are preferably weighted to allow for comparison of the alternative semantic interpretations outputted by a device.

    The structure employed here is the abstract meaning representation (AMR). We show that AMRs representing well-formed semantics can be generated while leaving out AMRs that are not semantically well-formed. For this purpose, we use a type of graph grammar called contextual hyperedge replacement grammar (CHRG). Moreover, we argue that a more well-known subclass of CHRG – the hyperedge replacement grammar (HRG) – is not powerful enough for AMR generation. This is due to the limitation of HRG when it comes to handling co-references, which in its turn depends on the fact that HRGs only generate graphs of bounded treewidth.

    Furthermore, we also address the N best problem, which is as follows: Given a weighted device, return the N best (here: smallest-weighted, or more intuitively, smallest-errored) structures. Our goal is to solve the N best problem for devices capable of expressing sophisticated forms of semantic representations such as CHRGs. Here, however, we merely take a first step consisting in developing methods for solving the N best problem for weighted tree automata and some types of weighted acyclic hypergraphs.

  • 440.
    Jonsson, Fredrik
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Bylund, Lisa
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Design of a Household Concept Motivating Sustainable Consumption Behavior2011Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In common households today the awareness of the electricity, water and waste consumption are rather low. This generates a behavior that conicts with the existing goals of sustainable living. Together with Stockholm City and other companies The Interactive Institute is working with a project called Stockholm Royal Seaport, where the goal is to implement a solution for how smart grids and visualizations in the household could motivate a change of this behavior. This master thesis examines how to do this using an in-home display and ambient interfaces in an apartment. In order to motivate the users the goal was to create a dynamic and exploring solution, that would not cause them to loose interest. The result was an in-home display interface based on dynamic home screens, social comparison and achievements, and a couple of ambient interfaces located in the household. A presentation video was made in order to visualize the coherent solution.

  • 441.
    Jäger, Gerold
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Drewes, Frank
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    The Metric Dimension of Zn × Zn × Zn is ⌊3n/2⌋2019Inngår i: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, , s. 78Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work we determine the metric dimension of Zn × Zn × Zn as ⌊3n/2⌋ for all n ≥ 2. We prove this result by investigating a variant of Mastermind.

    Mastermind is a famous two-player game that has attracted much attention in the literature in recent years. In particular we consider the static (also called non-adaptive) black-peg variant of Mastermind. The game is played by a codemaker and a codebreaker. Given c colors and p pegs, the principal rule is that the codemaker has to choose a secret by assigning colors to the pegs, i.e., the secret is a p-tuple of colors, and the codebreaker asks a number of questions all at once. Like the secret, a question is a p-tuple of colors chosen from the c available colors. The codemaker then answers all of those questions by telling the codebreaker how many pegs in each question are correctly colored. The goal is to find the minimal number of questions that allows the codebreaker to determine the secret from the received answers. We present such a strategy for this game for p = 3 pegs and an arbitrary number c ≥ 2 of colors using ⌊3c/2⌋ + 1 questions, which we prove to be both feasible and optimal.

    The minimal number of questions required for p pegs and c colors is easily seen to be equal to the metric dimension of Zpc plus 1 which proves our main result.

  • 442.
    Kallin Westin, Lena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Preprocessing perceptrons2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Reliable results are crucial when working with medical decision support systems. A decision support system should be reliable but also be interpretable, i.e. able to show how it has inferred its conclusions. In this thesis, the preprocessing perceptron is presented as a simple but effective and efficient analysis method to consider when creating medical decision support systems. The preprocessing perceptron has the simplicity of a perceptron combined with a performance comparable to the multi-layer perceptron.

    The research in this thesis has been conducted within the fields of medical informatics and intelligent computing. The original idea of the production line as a tool for a domain expert to extract information, build decision support systems and integrate them in the existing system is described. In the introductory part of the thesis, an introduction to feed-forward neural networks and fuzzy logic is given as a background to work with the preprocessing perceptron. Input to a decision support system is crucial and it is described how to gather a data set, decide how many and what kind of inputs to use. Outliers, errors and missing data are covered as well as normalising of the input. Training is done in a backpropagation-like manner where the division of the data set into a training and a test set can be done in several different ways just as the training itself can have variations. Three major groups of methods to estimate the discriminance effect of the preprocessing perceptron are described and a discussion of the trade-off between complexity and approximation strength are included.

    Five papers are presented in this thesis. Case studies are shown where the preprocessing perceptron is compared to multi-layer perceptrons, statistical approaches and other mathematical models. The model is extended to a generalised preprocessing perceptron and the performance of this new model is compared to the traditional feed-forward neural networks. Results concerning the preprocessing layer and its connection to multivariate decision limits are included. The well-known ROC curve is described and introduced fully into the field of computer science as well as the improved curve, the QROC curve. Finally a tutorial to the program trainGPP is presented. It describes how to work with the preprocessing perceptron from the moment when a data file is provided to the moment when a new decision support system is built.

  • 443.
    Kallin Westin, Lena
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Nordström, Marie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Supplemental Instruction (SI) - Applied on the course Object-Oriented Programming Methodology2003Rapport (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The introduction of the Supplemental Instruction (SI) method to the introductory programming course was initialised by the fact that the rate of students passing the course had been constantly decreasing for the last few years. This, in combination with the decreasing in student admission, made it necessary to further assist the students in some way. This was done during the autumn of 2002 and this paper describes the work concerning the entire SI-project.

  • 444.
    Kampik, Timotheus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Signavio GmbH, Berlin, Germany.
    Malhi, Avleen
    Department of Computer Science, Aalto University, Helsinki, Finland.
    Främling, Kary
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Agent-based Business Process Orchestration for IoT2019Inngår i: WI '19 IEEE/WIC/ACM International Conference on Web Intelligence / [ed] Payam Barnaghi, Georg Gottlob, Yannis Manolopoulos, Theodoros Tzouramanis, Athena Vakali, New York: ACM Press, 2019, s. 393-397Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The so-called Internet of Things is of increasing importance for facilitating productivity across industries, i.e., by connecting sensors with manufacturing lines and IT system landscapes with an increasing degree of autonomy. In this context, a common challenge is enabling reasonable trade-offs between structure and control on the one hand and flexibility and human-like intelligent behavior on the other hand. To address this challenge, we establish the need for and requirements of a hybrid IoT-/agent-based business process orchestration architecture that utilizes open standards. We propose a four-layered architecture, which integrates autonomous agents and business process orchestration for IoT/agents, and provide a running example for a supply chain management (purchasing) use case.

  • 445.
    Kampik, Timotheus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap. Signavio GmbH, Berlin.
    Najjar, Amro
    Simulating, Off-Chain and On-Chain: Agent-Based Simulations in Cross-Organizational Business Processes2020Inngår i: Information, E-ISSN 2078-2489, Vol. 11, nr 1, artikkel-id 34Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Information systems execute increasingly complex business processes, often across organizations. Blockchain technology has emerged as a potential facilitator of (semi)-autonomous cross-organizational business process execution; in particular, so-called consortium blockchains can be considered as promising enablers in this context, as they do not require the use of cryptocurrency-based blockchain technology, as long as the trusted (authenticated) members of the network are willing to provide computing resources for consensus-finding. However, increased autonomy in the execution of business processes also requires the delegation of business decisions to machines. To support complex decision-making processes by assessing potential future outcomes, agent-based simulations can be considered a useful tool for the autonomous enterprise. In this paper, we explore the intersection of multi-agent simulations and consortium blockchain technology in the context of enterprise applications by devising architectures and technology stacks for both off-chain and on-chain agent-based simulation in the context of blockchain-based business process execution.

  • 446.
    Kampik, Timotheus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Najjar, Amro
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Calvaresi, Davide
    University of Applied Science Western Switzerland.
    MAS-Aided Approval for Bypassing Decentralized Processes: an Architecture2018Inngår i: 2018 IEEE/WIC/ACM International Conference on Web Intelligence (WI), IEEE Computer Society, 2018, s. 713-718Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Executing business processes in a decentralized manner can improve inter-organizational efficacy. For example, blockchain-based process execution allows, at least conceptually, for cross-organizational compatibility, data integration, and integrity assurance without the need for a centralized trusted operator. However, most business processes run in agile and rapidly changing business environments. Updating a decentralized process requires continuous and extensive consensus-building efforts. Reflecting all organizations' business requirements is hardly practicable. Hence, in many real-life scenarios, to support cases with initially unforeseen properties, organizations can allow to bypass the decentralized process and fall-back to local variants. Yet, the decision to bypass or update a given process can have significant social implications since it may encourage a social dynamic that encourages collective avoidance of the decentralized process. This paper proposes a multi-agent simulation system to assess the social consequences of approving a bypass under given conditions. The proposed simulation is intended to inform the decision-maker (human or machine) on whether to allow to bypass a process or not. Moreover, we present an architecture for the integration of multi-agent simulation system, local process engine, and decentralized process execution environment, and describe a possible implementation with a particular tool chain.

  • 447.
    Kampik, Timotheus
    et al.
    Umeå universitet.
    Nieves, Juan Carlos
    Umeå universitet.
    JS-son - A Minimal JavaScript BDI Agent Library2019Inngår i: EMAS 2019: Accepted Papers, Centre for Autonomous systems technology, University of Liverpool , 2019Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    There is a multitude of agent-oriented software engineering frame-works available, most of them produced by the academic multi-agent systemscommunity. However, these frameworks often impose programming paradigmson their users that are hard to learn for engineers who are used to modern high-level programming languages such as JavaScript and Python. To show how theadoption of agent-oriented programming by the software engineering mainstreamcan be facilitated, we provide an early, simplistic JavaScript library prototype forimplementing belief-desire-intention (BDI) agents. The library focuses on thecore BDI concepts and refrains from imposing further restrictions on the pro-gramming approach. To illustrate its usefulness, we demonstrate how the librarycan be used for multi-agent systems simulations on the web, as well as embeddedin Python-based data science tools.

  • 448.
    Kampik, Timotheus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Nieves, Juan Carlos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindgren, Helena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Coercion and deception in persuasive technologies2018Inngår i: Proceedings of the 20th International Trust Workshop / [ed] Robin Cohen, Murat Sensoy, Timothy J. Norman, CEUR-WS , 2018, s. 38-49Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Technologies that shape human behavior are of high societal relevance, both when considering their current impact and their future potential. In information systems research and in behavioral psychology, such technologies are typically referred to as persuasive technologies. Traditional definitions like the ones created by Fogg, and Harjumaa and Oinas-Kukkonen, respectively, limit the scope of persuasive technology to non-coercive, non-deceptive technologies that are explicitly designed for persuasion. In this paper we analyze existing technologies that blur the line between persuasion, deception,and coercion. Based on the insights of the analysis, we lay down an updated definition of persuasive technologies that includes coercive and deceptive forms of persuasion. Our definition also accounts for persuasive functionality that was not designed by the technology developers. We argue that this definition will help highlight ethical and societal challenges related to technologies that shape human behavior and encourage research that solves problems with technology-driven persuasion. Finally, we suggest multidisciplinary research that can help address the challenges our definition implies. The suggestions we provide range from empirical studies to multi-agent system theory.

  • 449.
    Kampik, Timotheus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Nieves, Juan Carlos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindgren, Helena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Empathic autonomous agents2019Inngår i: Engineering multi-agent systems: 6th international workshop, EMAS 2018, Stockholm, Sweden, July 14-15, 2018, revised selected papers / [ed] Danny Weyns, Viviana Mascardi and Alessandro Ricci, Cham: Springer, 2019, 6, s. 181-201Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Identifying and resolving conflicts of interests is a key challenge when designing autonomous agents. For example, such conflicts often occur when complex information systems interact persuasively with humans and are in the future likely to arise in non-human agent-to-agent interaction. We introduce a theoretical framework for an empathic autonomous agent that proactively identifies potential conflicts of interests in interactions with other agents (and humans) by considering their utility functions and comparing them with its own preferences using a system of shared values to find a solution all agents consider acceptable. To illustrate how empathic autonomous agents work, we provide running examples and a simple prototype implementation in a general-purpose programing language. To give a high-level overview of our work, we propose a reasoning-loop architecture for our empathic agent.

  • 450.
    Kampik, Timotheus
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Nieves, Juan Carlos
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Lindgren, Helena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Explaining Sympathetic Actions of Rational Agents2019Inngår i: Explainable, Transparent Autonomous Agents and Multi-Agent Systems: First International Workshop, EXTRAAMAS 2019, Montreal, QC, Canada, May 13–14, 2019, Revised Selected Papers / [ed] Calvaresi, Davide, Najjar, Amro, Schumacher, Michael och Främling, Kary, Cham: Springer, 2019, s. 59-76Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Typically, humans do not act purely rationally in the sense of classic economic theory. Different patterns of human actions have been identified that are not aligned with the traditional view of human actors as rational agents that act to maximize their own utility function. For instance, humans often act sympathetically -- i.e., they choose actions that serve others in disregard of their egoistic preferences. Even if there is no immediate benefit resulting from a sympathetic action, it can be beneficial for the executing individual in the long run. This paper builds upon the premise that it can be beneficial to design autonomous agents that employ sympathetic actions in a similar manner as humans do. We create a taxonomy of sympathetic actions, that reflects different goal types an agent can have to act sympathetically. To ensure that the sympathetic actions are recognized as such, we propose different explanation approaches autonomous agents may use. In this context, we focus on human-agent interaction scenarios. As a first step towards an empirical evaluation, we conduct a preliminary human-robot interaction study that investigates the effect of explanations of (somewhat) sympathetic robot actions on the human participants of human-robot ultimatum games. While the study does not provide statistically significant findings (but notable differences), it can inform future in-depth empirical evaluations.

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