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  • 1.
    Aghighi, Meysam
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Computational Complexity of some Optimization Problems in Planning2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Automated planning is known to be computationally hard in the general case. Propositional planning is PSPACE-complete and first-order planning is undecidable. One method for analyzing the computational complexity of planning is to study restricted subsets of planning instances, with the aim of differentiating instances with varying complexity. We use this methodology for studying the computational complexity of planning. Finding new tractable (i.e. polynomial-time solvable) problems has been a particularly important goal for researchers in the area. The reason behind this is not only to differentiate between easy and hard planning instances, but also to use polynomial-time solvable instances in order to construct better heuristic functions and improve planners. We identify a new class of tractable cost-optimal planning instances by restricting the causal graph. We study the computational complexity of oversubscription planning (such as the net-benefit problem) under various restrictions and reveal strong connections with classical planning. Inspired by this, we present a method for compiling oversubscription planning problems into the ordinary plan existence problem. We further study the parameterized complexity of cost-optimal and net-benefit planning under the same restrictions and show that the choice of numeric domain for the action costs has a great impact on the parameterized complexity. We finally consider the parameterized complexity of certain problems related to partial-order planning. In some applications, less restricted plans than total-order plans are needed. Therefore, a partial-order plan is being used instead. When dealing with partial-order plans, one important question is how to achieve optimal partial order plans, i.e. having the highest degree of freedom according to some notion of flexibility. We study several optimization problems for partial-order plans, such as finding a minimum deordering or reordering, and finding the minimum parallel execution length.

    List of papers
    1. Oversubscription planning: Complexity and compilability
    Open this publication in new window or tab >>Oversubscription planning: Complexity and compilability
    2014 (English)In: Proceedings of the Twenty-Eighth AAAI Conference on Artificial Intelligence, AI Access Foundation , 2014, Vol. 3, 2221-2227 p.Conference paper, Published paper (Refereed)
    Abstract [en]

    Many real-world planning problems are oversubscription problems where all goals are not simultaneously achievable and the planner needs to find a feasible subset. We present complexity results for the so-called partial satisfaction and net benefit problems under various restrictions; this extends previous work by van den Briel et al. Our results reveal strong connections between these problems and with classical planning. We also present a method for efficiently compiling oversubscription problems into the ordinary plan existence problem; this can be viewed as a continuation of earlier work by Keyder and Geffner.

    Place, publisher, year, edition, pages
    AI Access Foundation, 2014
    National Category
    Computer and Information Science
    Identifiers
    urn:nbn:se:liu:diva-116727 (URN)2-s2.0-84908192348 (Scopus ID)9781577356790 (ISBN)
    Conference
    28th AAAI Conference on Artificial Intelligence, AAAI 2014, 26th Innovative Applications of Artificial Intelligence Conference, IAAI 2014 and the 5th Symposium on Educational Advances in Artificial Intelligence, EAAI 2014
    Available from: 2015-04-09 Created: 2015-04-02 Last updated: 2017-05-17
    2. Tractable Cost-Optimal Planning over Restricted Polytree Causal Graphs
    Open this publication in new window or tab >>Tractable Cost-Optimal Planning over Restricted Polytree Causal Graphs
    2015 (English)In: Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence, AAAI Press, 2015Conference paper, Published paper (Refereed)
    Abstract [en]

    Causal graphs are widely used to analyze the complexity of planning problems. Many tractable classes have been identified with their aid and state-of-the-art heuristics have been derived by exploiting such classes. In particular, Katz and Keyder have studied causal graphs that are hourglasses (which is a generalization of forks and inverted-forks) and shown that the corresponding cost-optimal planning problem is tractable under certain restrictions. We continue this work by studying polytrees (which is a generalization of hourglasses) under similar restrictions. We prove tractability of cost-optimal planning by providing an algorithm based on a novel notion of variable isomorphism. Our algorithm also sheds light on the k-consistency procedure for identifying unsolvable planning instances. We speculate that this may, at least partially, explain why merge-and-shrink heuristics have been successful for recognizing unsolvable instances.

    Place, publisher, year, edition, pages
    AAAI Press, 2015
    Series
    Proceedings of the AAAI Conference on Artificial Intelligence, ISSN 2159-5399, E-ISSN 2374-3468
    Keyword
    automated planning, causal graph, polynomial-time algorithm, cost-optimal planning, polytree
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-118729 (URN)978-1-57735-703-2 (ISBN)
    Conference
    29th AAAI Conference on Artificial Intelligence (AAAI-15), January 25–30, Austin, TX, USA
    Funder
    CUGS (National Graduate School in Computer Science)
    Available from: 2015-06-03 Created: 2015-06-03 Last updated: 2017-05-17
    3. Cost-optimal and Net-benefit Planning--A Parameterised Complexity View
    Open this publication in new window or tab >>Cost-optimal and Net-benefit Planning--A Parameterised Complexity View
    2015 (English)In: 24th International Joint Conference on Artificial Intelligence (IJCAI-15), 2015Conference paper, Published paper (Refereed)
    Abstract [en]

    Cost-optimal planning (COP) uses action costs and asks for a minimum-cost plan. It is sometimes assumed that there is no harm in using actions with zero cost or rational cost. Classical complexity analysis does not contradict this assumption; planning is PSPACE-complete regardless of whether action costs are positive or non-negative, integer or rational. We thus apply parameterised complexity analysis to shed more light on this issue. Our main results are the following. COP is W[2]-complete for positive integer costs, i.e. it is no harder than finding a minimum-length plan, but it is para-NPhard if the costs are non-negative integers or positive rationals. This is a very strong indication that the latter cases are substantially harder. Net-benefit planning (NBP) additionally assigns goal utilities and asks for a plan with maximum difference between its utility and its cost. NBP is para-NP-hard even when action costs and utilities are positive integers, suggesting that it is harder than COP. In addition, we also analyse a large number of subclasses, using both the PUBS restrictions and restricting the number of preconditions and effects.

    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-128181 (URN)9781577357384 (ISBN)
    Conference
    24th International Joint Conference on Artificial Intelligence (IJCAI-15)
    Funder
    CUGS (National Graduate School in Computer Science), 1054Swedish Research Council, 621- 2014-4086
    Available from: 2016-05-20 Created: 2016-05-20 Last updated: 2017-10-06Bibliographically approved
    4. A Multi-parameter Complexity Analysis of Cost-optimal and Net-benefit Planning
    Open this publication in new window or tab >>A Multi-parameter Complexity Analysis of Cost-optimal and Net-benefit Planning
    2016 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    Aghighi and Bäckström have previously studied cost-optimal planning (COP) and net-benefit planning (NBP) for three action cost domains: the positive integers (Z_+), the non-negative integers (Z_0) and the positive rationals (Q_+). These were indistinguishable under standard complexity analysis for both problems, but separated for COP using parameterised complexity analysis. With the plan cost, k, as parameter, COP was W[2]-complete for Z_+, but para-NP-hard for both Z_0 and Q_+, i.e. presumably much harder. NBP was para-NP-hard for all three domains, thus remaining unseparable. We continue by considering combinations with several additional parameters and also the non-negative rationals (Q_0). Examples of new parameters are the plan length, l, and the largest denominator of the action costs, d. Our findings include: (1) COP remains W[2]-hard for all domains, even if combining all parameters; (2) COP for Z_0 is in W[2] for the combined parameter {k,l}; (3) COP for Q_+ is in W[2] for {k,d} and (4) COP for Q_0 is in W[2] for {k,d,l}. For NBP we consider further additional parameters, where the most crucial one for reducing complexity is the sum of variable utilities. Our results help to understand the previous results, eg. the separation between Z_+ and Q_+ for COP, and to refine the previous connections with empirical findings.

    Place, publisher, year, edition, pages
    AAAI Press, 2016
    Keyword
    cost-optimal planning, parameterised complexity, numeric domains
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-136278 (URN)9781577357575 (ISBN)
    Conference
    Twenty-Sixth International Conference on Automated Planning and Scheduling (ICAPS-16)
    Available from: 2017-04-05 Created: 2017-04-05 Last updated: 2017-10-06
    5. Plan Reordering and Parallel Execution -- A Parameterized Complexity View
    Open this publication in new window or tab >>Plan Reordering and Parallel Execution -- A Parameterized Complexity View
    2017 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    Bäckström has previously studied a number of optimization problems for partial-order plans, like finding a minimum deordering (MCD) or reordering (MCR), and finding the minimum parallel execution length (PPL), which are all NP-complete. We revisit these problems, but applying parameterized complexity analysis rather than standard complexity analysis. We consider various parameters, including both the original and desired size of the plan order, as well as its width and height. Our findings include that MCD and MCR are W[2]-hard and in W[P] when parameterized with the desired order size, and MCD is fixed-parameter tractable (fpt) when parameterized with the original order size. Problem PPL is fpt if parameterized with the size of the non-concurrency relation, but para-NP-hard in most other cases. We also consider this problem when the number (k) of agents, or processors, is restricted, finding that this number is a crucial parameter; this problem is fixed-parameter tractable with the order size, the parallel execution length and k as parameter, but para-NP-hard without k as parameter.

    Place, publisher, year, edition, pages
    AAAI Press, 2017
    Keyword
    Partially ordered plan, Parameterized complexity, Complexity of planning, Plan reordering, Parallel plan execution
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-136279 (URN)
    Conference
    Thirty-First AAAI Conference on Artificial Intelligence (AAAI-17)
    Available from: 2017-04-05 Created: 2017-04-05 Last updated: 2017-05-17Bibliographically approved
  • 2.
    Aghighi, Meysam
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Bäckström, Christer
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    A Multi-parameter Complexity Analysis of Cost-optimal and Net-benefit Planning2016Conference paper (Refereed)
    Abstract [en]

    Aghighi and Bäckström have previously studied cost-optimal planning (COP) and net-benefit planning (NBP) for three action cost domains: the positive integers (Z_+), the non-negative integers (Z_0) and the positive rationals (Q_+). These were indistinguishable under standard complexity analysis for both problems, but separated for COP using parameterised complexity analysis. With the plan cost, k, as parameter, COP was W[2]-complete for Z_+, but para-NP-hard for both Z_0 and Q_+, i.e. presumably much harder. NBP was para-NP-hard for all three domains, thus remaining unseparable. We continue by considering combinations with several additional parameters and also the non-negative rationals (Q_0). Examples of new parameters are the plan length, l, and the largest denominator of the action costs, d. Our findings include: (1) COP remains W[2]-hard for all domains, even if combining all parameters; (2) COP for Z_0 is in W[2] for the combined parameter {k,l}; (3) COP for Q_+ is in W[2] for {k,d} and (4) COP for Q_0 is in W[2] for {k,d,l}. For NBP we consider further additional parameters, where the most crucial one for reducing complexity is the sum of variable utilities. Our results help to understand the previous results, eg. the separation between Z_+ and Q_+ for COP, and to refine the previous connections with empirical findings.

  • 3.
    Aghighi, Meysam
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Bäckström, Christer
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Plan Reordering and Parallel Execution -- A Parameterized Complexity View2017Conference paper (Refereed)
    Abstract [en]

    Bäckström has previously studied a number of optimization problems for partial-order plans, like finding a minimum deordering (MCD) or reordering (MCR), and finding the minimum parallel execution length (PPL), which are all NP-complete. We revisit these problems, but applying parameterized complexity analysis rather than standard complexity analysis. We consider various parameters, including both the original and desired size of the plan order, as well as its width and height. Our findings include that MCD and MCR are W[2]-hard and in W[P] when parameterized with the desired order size, and MCD is fixed-parameter tractable (fpt) when parameterized with the original order size. Problem PPL is fpt if parameterized with the size of the non-concurrency relation, but para-NP-hard in most other cases. We also consider this problem when the number (k) of agents, or processors, is restricted, finding that this number is a crucial parameter; this problem is fixed-parameter tractable with the order size, the parallel execution length and k as parameter, but para-NP-hard without k as parameter.

  • 4.
    Aghighi, Meysam
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Jonsson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Ståhlberg, Simon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Tractable Cost-Optimal Planning over Restricted Polytree Causal Graphs2015In: Proceedings of the Twenty-Ninth AAAI Conference on Artificial Intelligence, AAAI Press, 2015Conference paper (Refereed)
    Abstract [en]

    Causal graphs are widely used to analyze the complexity of planning problems. Many tractable classes have been identified with their aid and state-of-the-art heuristics have been derived by exploiting such classes. In particular, Katz and Keyder have studied causal graphs that are hourglasses (which is a generalization of forks and inverted-forks) and shown that the corresponding cost-optimal planning problem is tractable under certain restrictions. We continue this work by studying polytrees (which is a generalization of hourglasses) under similar restrictions. We prove tractability of cost-optimal planning by providing an algorithm based on a novel notion of variable isomorphism. Our algorithm also sheds light on the k-consistency procedure for identifying unsolvable planning instances. We speculate that this may, at least partially, explain why merge-and-shrink heuristics have been successful for recognizing unsolvable instances.

  • 5.
    Ahlgren, Simon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Aini, Daniel
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Conversion and Analysis of Telemetric Data from the CCSDS Standard2017Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    When communicating with spacecrafts, the international standard is to use the protocols defined by CCSDS. In this study, the Space Packet Protocol from CCSDS is converted to the Digital Recording Standard used in aviation. The goal of the study is to find out in what way such a conversion can be made, as well as analyzing the efficiency of different packing methods for the Digital Recording Standard. An application is developed in order to perform the conversion, and the performance of said application is profiled using different packet sizes. In the end the results are evaluated and an optimal packet size is found in terms of runtime and memory usage. In the end we conclude that a packet size of 216 bytes is best when prioritizing speed, and a packet size of 219 bytes is best when prioritizing memory.

  • 6.
    Al-egli, Muntaher
    et al.
    Linköping University, Department of Computer and Information Science.
    Zeidan Nasser, Adham
    Linköping University, Department of Computer and Information Science.
    Identifiering av anomalier i COSMIC genom analys av loggar2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Logs are an important part of any system; it provides an insight into what is happening. One of the biggest trends in the IT industry is analyzing logs and extracting essential information. The information in the logs are valuable resources that can be used to detect anomalies and manage them before it affects the user

    In this thesis we will dive into the basics of the information retrieval and analyze exceptions in the logs from COSMIC to investigate whether it is feasible to detect anomalies using retrospective data. This thesis also gives an insight into whether it’s possible to visualize data from logs and offer a powerful search engine. Therefore we will dive into the three well known applications that addresses the issues in centralized logging: Elasticsearch, Logstash and Kibana.

    In summary, our results shows that it’s possible to detected anomalies by applying statistical methods on both in retrospective and real time data.

  • 7.
    Alhowaidi, Mohammad
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, The Institute of Technology.
    Real-Time Systems with Radiation-Hardened Processors: A GPU-based Framework to Explore Tradeoffs2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Radiation-hardened processors are designed to be resilient against soft errorsbut such processors are slower than Commercial Off-The-Shelf (COTS)processors as well significantly costlier. In order to mitigate the high costs,software techniques such as task re-executions must be deployed together withadequately hardened processors to provide reliability. This leads to a huge designspace comprising of the hardening level of the processors and the numberof re-executions of each task in the system. Each configuration in this designspace represents a tradeoff between processor load, reliability and costs.

    The reliability comes at the price of higher costs due to higher levels of hardeningand performance degradation due to hardening or due to re-executions.Thus, the tradeoffs between performance, reliability and costs must be carefullystudied. Pertinent questions that arise in such a design scenario are — (i)how many times a task must be re-executed and (ii) what should be hardeninglevel? — such that the system reliability is satisfied.

    In order to evaluate such tradeoffs efficiently, in this thesis, we proposenovel framework that harnesses the computational power of Graphics ProcessingUnits (GPUs). Our framework is based on a system failure probabilityanalysis that connects the probability of failure of tasks to the overall systemreliability. Based on characteristics of this probabilistic analysis as well asreal-time deadlines, we derive bounds on the design space to prune infeasiblesolutions. Finally, we illustrate the benefits of our proposed framework withseveral experiments

  • 8.
    Ali, Akhtar
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Dastgeer, Usman
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    OpenCL for programming shared memory multicore CPUs2011In: Fourth Swedish Workshop on Multi-Core Computing MCC-2011: November 23-25, 2011, Linköping University, Linköping, Sweden / [ed] Christoph Kessler, Linköping: Linköping University , 2011, Vol. S. 65-70, 65-70 p.Conference paper (Other academic)
    Abstract [en]

    In this work, we evaluate the effectiveness of OpenCL for programming multicore CPUs in a comparative case study with OpenMP and Intel TBB for five benchmark applications: matrix multiply, LU decomposition, 2D image convolution, Pi value approximation and image histogram generation.

  • 9.
    Almquist, Mathias
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Almquist, Viktor
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    A study on Android games: 3G energy consumption, CPU-utilization and system calls2015Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    The popularity of mobile games has increased drastically during the recent years andmany people use them as their main source of entertainment. Mobile gamescommunicate with other devices over the network which consumes a lot of energy,especially when connected to cellular networks (e.g., 3G). This high energy expensecan feel unjustified to the player since always-on network connectivity is not requiredin order to play most games.Furthermore, the number of malware-infected applications in offical applicationstores has increased significantly in the recent years. These malware-infectedapplications can gain unrestricted access and control of users phones which can be athreat to security. Information about the behaviour characteristics of games can beused to develop or improve systems for detecting malware applications.In this thesis, 20 popular Android games are analysed with a focus on the datacommunication, CPU utilization and system call behaviour. The main subject of thedata communication study is the 3G communication energy consumed by games. Thesystem call study aims at quantifying the number and type of calls used by games.This may be useful in a further study of harmful behaviour by apps.The profiling results presented in this report show that the communication energyvaries drastically among games. Games with a very similar gameplay can consumevery different amounts of energy which indicates that there is room for improvementsin many of the games. Ad-free games consume significantly less energy than gamesthat use in-app advertisements. The results show that improving the advertisementfetching policy could reduce the energy consumption of these games. The majority ofthe games can be played without network connectivity and therefore thecommunication energy consumed could be completely avoided. The thesis alsoshows that games use a wide variety of system calls and that many of the system callsare common among the games.

  • 10.
    Alnervik, Erik
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Evaluation of the Configurable Architecture REPLICA with Emulated Shared Memory2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    REPLICA is a family of novel scalable chip multiprocessors with configurable emulated shared memory architecture, whose computation model is based on the PRAM (Parallel Random Access Machine) model.

    The purpose of this thesis is to, by benchmarking different types of computation problems on REPLICA, similar parallel architectures (SB-PRAM and XMT) and more diverse ones (Xeon X5660 and Tesla M2050), evaluate how REPLICA is positioned among other existing architectures, both in performance and programming effort. But it should also examine if REPLICA is more suited for any special kinds of computational problems.

    By using some of the well known Berkeley dwarfs, and input from unbiased sources, such as The University of Florida Sparse Matrix Collection and Rodinia benchmark suite, we have made sure that the benchmarks measure relevant computation problems.

    We show that today’s parallel architectures have some performance issues for applications with irregular memory access patterns, which the REPLICA architecture can solve. For example, REPLICA only need to be clocked with a few MHz to match both Xeon X5660 and Tesla M2050 for the irregular memory access benchmark breadth first search. By comparing the efficiency of REPLICA to a CPU (Xeon X5660), we show that it is easier to program REPLICA efficiently than today’s multiprocessors.

  • 11.
    Al-Trad, Anas
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Optimized Composition of Parallel Components on a Linux Cluster2012Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    We develop a novel framework for optimized composition of explicitly parallel software components with different implementation variants given the problem size, data distribution scheme and processor group size on a Linux cluster. We consider two approaches (or two cases of the framework). 

    In the first approach, dispatch tables are built using measurement data obtained offline by executions for some (sample) points in the ranges of the context properties. Inter-/extrapolation is then used to do actual variant-selection for a given execution context at run-time.

    In the second approach, a cost function of each component variant is provided by the component writer for variant-selection. These cost functions can internally lookup measurements' tables built, either offline or at deployment time, for computation- and communication-specific primitives.

    In both approaches, the call to an explicitly parallel software component (with different implementation variants) is made via a dispatcher instead of calling a variant directly.

    As a case study, we apply both approaches on a parallel component for matrix multiplication with multiple implementation variants. We implemented our variants using Message Passing Interface (MPI). The results show the reduction in execution time for the optimally composed applications compared to applications with hard-coded composition. In addition, the results show the comparison of estimated and measured times for each variant using different data distributions, processor group and problem sizes.

  • 12.
    Alvila, Markus
    et al.
    Linköping University, Department of Computer and Information Science.
    Johansson, Jonathan
    Linköping University, Department of Computer and Information Science.
    Johansson, Philip
    Linköping University, Department of Computer and Information Science.
    Lenz, Silas
    Linköping University, Department of Computer and Information Science.
    Lindmark, Sebastian
    Linköping University, Department of Computer and Information Science.
    Norberg, Emil
    Linköping University, Department of Computer and Information Science.
    Regard, Viktor
    Linköping University, Department of Computer and Information Science.
    Övervakning och bedömning av flygledares prestanda2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 13.
    Aminifar, Amir
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Analysis, Design, and Optimization of Embedded Control Systems2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Today, many embedded or cyber-physical systems, e.g., in the automotive domain, comprise several control applications, sharing the same platform. It is well known that such resource sharing leads to complex temporal behaviors that degrades the quality of control, and more importantly, may even jeopardize stability in the worst case, if not properly taken into account.

    In this thesis, we consider embedded control or cyber-physical systems, where several control applications share the same processing unit. The focus is on the control-scheduling co-design problem, where the controller and scheduling parameters are jointly optimized. The fundamental difference between control applications and traditional embedded applications motivates the need for novel methodologies for the design and optimization of embedded control systems. This thesis is one more step towards correct design and optimization of embedded control systems.

    Offline and online methodologies for embedded control systems are covered in this thesis. The importance of considering both the expected control performance and stability is discussed and a control-scheduling co-design methodology is proposed to optimize control performance while guaranteeing stability. Orthogonal to this, bandwidth-efficient stabilizing control servers are proposed, which support compositionality, isolation, and resource-efficiency in design and co-design. Finally, we extend the scope of the proposed approach to non-periodic control schemes and address the challenges in sharing the platform with self-triggered controllers. In addition to offline methodologies, a novel online scheduling policy to stabilize control applications is proposed.

  • 14.
    Aminifar, Amir
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Self-Triggered Controllers, Resource Sharing, and Hard Guarantees2016In: 2016 2ND INTERNATIONAL CONFERENCE ON EVENT-BASED CONTROL, COMMUNICATION, AND SIGNAL PROCESSING (EBCCSP), IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    Today, many control applications in embedded and cyber-physical systems are implemented on shared platforms, alongside other hard real-time or safety-critical applications. Having the resource shared among several applications, to provide hard guarantees, it is required to identify the amount of resource needed for each application. This is rather straightforward when the platform is shared among periodic control and periodic real-time applications. In the case of event-triggered and self-triggered controllers, however, the execution patterns and, in turn, the resource usage are not clear. Therefore, a major implementation challenge, when the platform is shared with self-triggered controllers, is to provide hard and efficient stability and schedulability guarantees for other applications. In this paper, we identify certain execution patterns for self-triggered controllers, using which we are able to provide hard and efficient stability guarantees for periodic control applications.

  • 15.
    Amlinger, Anton
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    An Evaluation of Clustering and Classification Algorithms in Life-Logging Devices2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Using life-logging devices and wearables is a growing trend in today’s society. These yield vast amounts of information, data that is not directly overseeable or graspable at a glance due to its size. Gathering a qualitative, comprehensible overview over this quantitative information is essential for life-logging services to serve its purpose.

    This thesis provides an overview comparison of CLARANS, DBSCAN and SLINK, representing different branches of clustering algorithm types, as tools for activity detection in geo-spatial data sets. These activities are then classified using a simple model with model parameters learned via Bayesian inference, as a demonstration of a different branch of clustering.

    Results are provided using Silhouettes as evaluation for geo-spatial clustering and a user study for the end classification. The results are promising as an outline for a framework of classification and activity detection, and shed lights on various pitfalls that might be encountered during implementation of such service.

  • 16.
    Anders, Söderholm
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Justus, Sörman
    Linköping University, Department of Computer and Information Science, Software and Systems.
    GPU-accelleration of image rendering and sorting algorithms with the OpenCL framework2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Today's computer systems often contains several different processing units aside from the CPU. Among these the GPU is a very common processing unit with an immense compute power that is available in almost all computer systems. How do we make use of this processing power that lies within our machines? One answer is the OpenCL framework that is designed for just this, to open up the possibilities of using all the different types of processing units in a computer system. This thesis will discuss the advantages and disadvantages of using the integrated GPU available in a basic workstation computer for computation of image processing and sorting algorithms. These tasks are computationally intensive and the authors will analyze if an integrated GPU is up to the task of accelerating the processing of these algorithms. The OpenCL framework makes it possible to run one implementation on different processing units, to provide perspective we will benchmark our implementations on both the GPU and the CPU and compare the results. A heterogeneous approach that combines the two above mentioned processing units will also be tested and discussed. The OpenCL framework is analyzed from a development perspective and what advantages and disadvantages it brings to the development process will be presented.

  • 17.
    Andersson, Anders
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering. Swedish National Road and Transport Research Institute (VTI), Linköping, Sweden.
    Extensions for Distributed Moving Base Driving Simulators2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modern vehicles are complex systems. Different design stages for such a complex system include evaluation using models and submodels, hardware-in-the-loop systems and complete vehicles. Once a vehicle is delivered to the market evaluation continues by the public. One kind of tool that can be used during many stages of a vehicle lifecycle is driving simulators.

    The use of driving simulators with a human driver is commonly focused on driver behavior. In a high fidelity moving base driving simulator it is possible to provide realistic and repetitive driving situations using distinctive features such as: physical modelling of driven vehicle, a moving base, a physical cabin interface and an audio and visual representation of the driving environment. A desired but difficult goal to achieve using a moving base driving simulator is to have behavioral validity. In other words, \A driver in a moving base driving simulator should have the same driving behavior as he or she would have during the same driving task in a real vehicle.".

    In this thesis the focus is on high fidelity moving base driving simulators. The main target is to improve the behavior validity or to maintain behavior validity while adding complexity to the simulator. One main assumption in this thesis is that systems closer to the final product provide better accuracy and are perceived better if properly integrated. Thus, the approach in this thesis is to try to ease incorporation of such systems using combinations of the methods hardware-in-the-loop and distributed simulation. Hardware-in-the-loop is a method where hardware is interfaced into a software controlled environment/simulation. Distributed simulation is a method where parts of a simulation at physically different locations are connected together. For some simulator laboratories distributed simulation is the only feasible option since some hardware cannot be moved in an easy way.

    Results presented in this thesis show that a complete vehicle or hardware-in-the-loop test laboratory can successfully be connected to a moving base driving simulator. Further, it is demonstrated that using a framework for distributed simulation eases communication and integration due to standardized interfaces. One identified potential problem is complexity in interface wrappers when integrating hardware-in-the-loop in a distributed simulation framework. From this aspect, it is important to consider the model design and the intersections between software and hardware models. Another important issue discussed is the increased delay in overhead time when using a framework for distributed simulation.

    List of papers
    1. Vehicle Powertrain Test Bench Co-Simulation with a Moving Base Simulator Using a Pedal Robot
    Open this publication in new window or tab >>Vehicle Powertrain Test Bench Co-Simulation with a Moving Base Simulator Using a Pedal Robot
    2013 (English)In: SAE International Journal of Passenger Cars - Electronic and Electrical Systems, ISSN 1946-4614, E-ISSN 1946-4622, Vol. 6, no 1, 169-179 p.Article in journal (Refereed) Published
    Abstract [en]

    To evaluate driver perception of a vehicle powertrain a moving base simulator is a well-established technique. We are connecting the moving base simulator Sim III, at the Swedish National Road and Transport Research Institute with a newly built chassis dynamometer at Vehicular Systems, Linköping University. The purpose of the effort is to enhance fidelity of moving base simulators by letting drivers experience an actual powertrain. At the same time technicians are given a new tool for evaluating powertrain solutions in a controlled environment. As a first step the vehicle model from the chassis dynamometer system has been implemented in Sim III. Interfacing software was developed and an optical fiber covering the physical distance of 500 m between the facilities is used to connect the systems. Further, a pedal robot has been developed that uses two linear actuators pressing the accelerator and brake pedals. The pedal robot uses feedback loops on accelerator position or brake cylinder pressure and is controlled via an UDP interface. Results from running the complete setup showed expected functionality and we are successful in performing a driving mission based on real road topography data. Vehicle acceleration and general driving feel was perceived as realistic by the test subjects while braking still needs improvements. The pedal robot construction enables use of a large set of cars available on the market and except for mounting the brake pressure sensor the time to switch vehicle is approximately 30 minutes.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-92215 (URN)10.4271/2013-01-0410 (DOI)
    Available from: 2013-05-08 Created: 2013-05-08 Last updated: 2017-04-07Bibliographically approved
    2. Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup
    Open this publication in new window or tab >>Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup
    2013 (English)In: Proceedings of the 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools; April 19, University of Nottingham, Nottingham, UK / [ed] Henrik Nilsson, Linköping: Linköping University Electronic Press, 2013, Vol. 84, 131-139 p.Conference paper, Published paper (Refereed)
    Abstract [en]

    A car model in Modelica has been developed to be used in a new setup for distributed real-time simulation where a moving base car simulator is connected with a real car in a chassis dynamometer via a 500m fiber optic communication link. The new co-simulator set-up can be used in a number of configurations where hardware in the loop can be interchanged with software in the loop. The models presented in this paper are the basic blocks chosen for modeling the system in the context of a distributed real-time simulation; estimating parameters for the powertrain model; the choice of numeric solver; and the interaction with the solver for real-time properties.

    Place, publisher, year, edition, pages
    Linköping: Linköping University Electronic Press, 2013
    Series
    Linköping Electronic Conference Proceedings, ISSN 1650-3686 (print), 1650-3740 (online) ; 84
    Keyword
    Modelica; real-time; distributed; communications link
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-118994 (URN)978-91-7519-621-3 (ISBN)978-91-7519-617-6 (ISBN)
    Conference
    The 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools, April 19, University of Nottingham, Nottingham; UK
    Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2017-04-07Bibliographically approved
    3. A Driving Simulation Platform using Distributed Vehicle Simulators and HLA
    Open this publication in new window or tab >>A Driving Simulation Platform using Distributed Vehicle Simulators and HLA
    Show others...
    2015 (English)In: Proceedings of the DSC 2015 Europe: Driving Simulation Conference & Exhibition / [ed] Heinrich Bülthoff, Andras Kemeny and Paolo Pretto, 2015, 123-130 p.Conference paper, Published paper (Refereed)
    Abstract [en]

    Modern vehicles are complex systems consisting of an increasing large multitude of components that operate together. While functional verification on individual components is important, it is also important to test components within a driving environment, both from a functional perspective and from a driver perspective. One proven way for testing is vehicle simulators and in this work the main goals have been to increase flexibility and scalability by introducing a distributed driving simulator platform.

    As an example, consider a workflow where a developer can go from a desktop simulation to an intermediate driving simulator to a high fidelity driving simulator with Hardware-In-the-Loop systems close to a finished vehicle in an easy way. To accomplish this, a distributed simulation architecture was designed and implemented that divides a driving simulator environment into four major entities with well-defined interfaces, using HLA as the method of communication. This platform was evaluated on two aspects, flexibility/scalability and timing performance. Results show that increased flexibility and scalability was achieved when using a distributed simulation platform. It is also shown that latency was only slightly increased when using HLA.

    Keyword
    Test, Vehicle, Engine, Performance, Simulator (driving), Computer
    National Category
    Computer Systems
    Research subject
    90 Road: Vehicles and vehicle technology, 911 Road: Components of the vehicle; 90 Road: Vehicles and vehicle technology, 96 Road: Vehicle operating and management
    Identifiers
    urn:nbn:se:liu:diva-136153 (URN)9783981309935 (ISBN)
    Conference
    Driving Simulation Conference 2015. 16-18 september 2015, Tübingen, Germany
    Available from: 2016-01-11 Created: 2017-03-31 Last updated: 2017-04-06Bibliographically approved
  • 18.
    Andersson, Anders
    et al.
    Statens väg- och transportforskningsinstitut, Fordonsteknik och simulering, FTS.
    Andersson Hultgren, Jonas
    Statens väg- och transportforskningsinstitut, Fordonsteknik och simulering, FTS.
    Leandertz, Rickard
    Hiq Accelerated Concept Evaluation AB, Stockholm, Sweden.
    Johansson, Martin
    Pitch Technologies.
    Eriksson, Steve
    Pitch Technologies.
    Jakobson, Ola
    Volvo Car Corporation.
    A Driving Simulation Platform using Distributed Vehicle Simulators and HLA2015In: Proceedings of the DSC 2015 Europe: Driving Simulation Conference & Exhibition / [ed] Heinrich Bülthoff, Andras Kemeny and Paolo Pretto, 2015, 123-130 p.Conference paper (Refereed)
    Abstract [en]

    Modern vehicles are complex systems consisting of an increasing large multitude of components that operate together. While functional verification on individual components is important, it is also important to test components within a driving environment, both from a functional perspective and from a driver perspective. One proven way for testing is vehicle simulators and in this work the main goals have been to increase flexibility and scalability by introducing a distributed driving simulator platform.

    As an example, consider a workflow where a developer can go from a desktop simulation to an intermediate driving simulator to a high fidelity driving simulator with Hardware-In-the-Loop systems close to a finished vehicle in an easy way. To accomplish this, a distributed simulation architecture was designed and implemented that divides a driving simulator environment into four major entities with well-defined interfaces, using HLA as the method of communication. This platform was evaluated on two aspects, flexibility/scalability and timing performance. Results show that increased flexibility and scalability was achieved when using a distributed simulation platform. It is also shown that latency was only slightly increased when using HLA.

  • 19.
    Andersson, Anders
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Swedish National Road and Transportation Research Institute.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Models for Distributed Real-Time Simulation in a Vehicle Co-Simulator Setup2013In: Proceedings of the 5th International Workshop on Equation-Based Object-Oriented Modeling Languages and Tools; April 19, University of Nottingham, Nottingham, UK / [ed] Henrik Nilsson, Linköping: Linköping University Electronic Press, 2013, Vol. 84, 131-139 p.Conference paper (Refereed)
    Abstract [en]

    A car model in Modelica has been developed to be used in a new setup for distributed real-time simulation where a moving base car simulator is connected with a real car in a chassis dynamometer via a 500m fiber optic communication link. The new co-simulator set-up can be used in a number of configurations where hardware in the loop can be interchanged with software in the loop. The models presented in this paper are the basic blocks chosen for modeling the system in the context of a distributed real-time simulation; estimating parameters for the powertrain model; the choice of numeric solver; and the interaction with the solver for real-time properties.

  • 20.
    Andersson, Daniel
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Integrated Test Environment2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To implement a command line interpreter is normally an easy task. The task getsharder when adding requirements of multi instance functions and the system is torun on a multi-processor security critical embedded system. This thesis describesa first iteration of the system development. The project behind the thesis consistsof requirement elicitation, design, implementation and unit testing. The resultfrom the project is a working first version of the system.

  • 21.
    Andersson, Erik Olov Mårten
    Linköping University, Department of Computer and Information Science.
    A Gameful Quest to Make Second Language Acquisition Fun2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study explores the application of principles from game design, and the motivational psychology it is founded upon, to the domain of second language acquisition. A gameful design process based on playtesting andanalysis with design lenses is adapted and used to iteratively design and develop a system for conversation practice with the goal of creating a motivating and engaging experience.The results indicate effectiveness of the process, but generalizing the results would require further research with bigger sample sizes and studies with varied core activities.

  • 22.
    Andersson, Filip
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Fault Diagnosis in Distributed Simulation Systems over Wide Area Networks using Active Probing2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The domain of distributed simulation is growing rapidly. This growth leads to larger and more complex supporting network architectures with high requirements on availability and reliability. For this purpose, efficient fault-monitoring is required. This work is an attempt to evaluate the viability of an Active probing approach in a distributed simulation system in a wide area network setting. In addition, some effort was directed towards building the probing-software with future extensions in mind. The Active probing approach was implemented and tested against certain performance requirements in a simulated environment. It was concluded that the approach is viable for detecting the health of the network components. However, additional research is required to draw a conclusion about the viability in more complicated scenarios that depend on more than the responsiveness of the nodes. The extensibility of the implemented software was evaluated with the QMOOD-metric and not deemed particularly extensible.

  • 23.
    Andersson, Fredrik
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Storing and structuring big data with businessintelligence in mind2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sectra has a customer database with approximately 1600 customers across the world. In this system there exists not only medical information but alsoinformation about the environment which the system runs in, usage  pattern and much more.

    This report is about storing data received from log les into a suitable database. Sectra wants to be able to analyze this information so that they can make strategic decisions and get a better understanding of their customers' needs. The tested databases are MongoDB, Cassandra, and MySQL. The results shows that MySQL  is not suitable for storing large amount of data with the current conguration. On the other hand, both MongoDB and Cassandra performed well with the growing amount of data.

  • 24.
    Andersson, Gustav
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, The Institute of Technology.
    Implementing touch interaction in a casual mobile game2014Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This thesis is to help developers in the touch design of casual games. The thesis work was made on the development platform Gideros Mobile and much of the thesis theory and methods will be based on that work. The purpose of the report is to show what one should think about when making a casual game in a touch design perspective, like taking into account that most people are used to one type of input design (like swiping or tapping), that you should design the game with the purpose to reach out to as a large audience as possible (taking into account people with disabilities) and some small notes on what should be avoided so not to deter people from wanting to play the game. It is important to note that this thesis is built for the purpose of mobile casual games, others will probably not find this thesis relevant.

  • 25.
    Andersson Holmström, Simon
    Linköping University, Department of Electrical Engineering, Computer Engineering.
    Adaptive TDC: Implementation and Evaluation of an FPGA2015Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Time to digital converter (TDC) is a digital unit that measures the time interval between two events.This is useful to determine the characteristics and patterns of a signal or an event. In this thesis ahybrid TDC is presented consisting of a tapped delay line and a clock counter principle.

    The TDC is used to measure the time between received data in a QKD application. If the measuredtime does not exceed a certain value then data had been sent without any interception. It is alsopossible to use TDCs in other fields such as laser-ranging and time-of-flight applications.

    The TDC consists of two carry chains, an encoder, a FIFO and a counter for each channel, anAXI-module and a control unit to generate command signals to all channels that are implemented.The time is measured by sampling the signal that has propagated through the carry chain and from thissample encode the propagation length.

    In this thesis a TDC is implemented that has a 10 ns dead time and a resolution below 28 psin a four channel mode. The propagation variation is approximately two percent of the total valueduring testing. For the implementation an FPGA-board with a Zynq XC7Z020 SoC is used withSystemVerilog that is a hardware describing language (HDL).

  • 26.
    Andersson, Håkan
    et al.
    Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering. Construct Tools PC AB, Sweden.
    Nordin, Peter
    Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering.
    Borrvall, Thomas
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Hilding, Daniel
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Schill, Mikael
    DYNAmore Nordic AB, Brigadgatan 5, S-58758 Linkoping, Sweden.
    Krus, Petter
    Linköping University, Department of Management and Engineering, Fluid and Mechatronic Systems. Linköping University, Faculty of Science & Engineering.
    Leidermark, Daniel
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units2017In: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663, Vol. 33, no 2, 317-333 p.Article in journal (Refereed)
    Abstract [en]

    This paper addresses a co-simulation method for fluid power driven machinery equipment, i.e. oil hydraulic machinery. In these types of machinery, the fluid-structure interaction affects the end-product performance to a large extent, hence an efficient co-simulation method is of high importance. The proposed method is based on a 1D system model representing the fluid components of the hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies. This means that the fluid system simulation will get a more accurate structural response, and that the structural simulation will get more correct fluid loads at every time step, compared to decoupled analysis. Global system parameters such as fluid flow, performance and efficiency can be evaluated from the 1D system model simulation results. From the 3D FE-models, it is possible to evaluate displacements, stresses and strains to be used in stress analysis, fatigue evaluation, acoustic analysis, etc. The method has been implemented using two well-known simulation tools for fluid power system simulations and FE-simulations, respectively, where the interface between the tools is realised by use of the Functional Mock-up Interface standard. A simple but relevant model is used to validate the method.

  • 27.
    Andersson, Rikard
    et al.
    Linköping University, Department of Computer and Information Science.
    Emberg, Johan
    Linköping University, Department of Computer and Information Science.
    Hazell, Sofie
    Linköping University, Department of Computer and Information Science.
    Laestander, Hjalmar
    Linköping University, Department of Computer and Information Science.
    Norberg, Gustaf
    Linköping University, Department of Computer and Information Science.
    Elmfeldt Rönnmark, Maximilian
    Linköping University, Department of Computer and Information Science.
    Buciuto Sundelin, Bruno
    Linköping University, Department of Computer and Information Science.
    Törngren, Erik
    Linköping University, Department of Computer and Information Science.
    Heat n' Eat: Utvecklingen av en användbar e-butik med fokus på navigerbarhet2017Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    Students today lack both time and money. At the same time e-commerce is increasing, and especially food sales over the internet. This report aims to explore the possibilities of a service that offers students a simple alternative for high quality food within their budget in the form of a web application. Students at Campus Valla expressed the need for such a service through a market research. The study was conducted by researching theories regarding usability and navigability. Students as a group often lack time and are used to getting fast and clear information; this is ensured by good navigability. After the researching of theories, several user tests were conducted on the targeted group. The result following this was the development of the web application Heat n' Eat. In order to achieve good navigability, the application was implemented with a simple layout, focusing on the products. A final user test showed that the application could be considered usable with focus on navigability.

  • 28.
    Andersson, Samuel
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Ekberg, Björn
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Prestandaoptimering av spelet Go Supernova2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Som underlag för den här rapporten använder vi oss av vårtspel Go Supernova. Det är skrivet i Java med hjälp avramverket LibGDX. Vi har undersökt hur man kan optimeraspelet för att kunna hantera så många objekt som möjligt menändå hålla ett bra spelflöde utan att förstöra den vision vihade när vi skapade spelet från första början. Vi har kommitfram till att ljusmotorn box2dlights använder sig av mycketprocessorkraft och användningen av den behövde justeras föratt tillfredsställa våra krav. Vi kommer även att tala omdesignval av spelets interna delar som gjorde att vi kundeundvika prestandaförluster.

  • 29.
    Asghar, Adeel
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Pfeiffer, Andreas
    DLR Institute of System Dynamic and Control, Wessling, Tyskland.
    Palanisamy, Arunkumar
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Mengist, Alachew
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sjölund, Martin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pop, Adrian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Automatic Regression Testing of Simulation Models and Concept for Simulation of Connected FMUs in PySimulator2015In: Proceedings of the 11th International Modelica Conference: Versailles, France, September 21-23, 2015 / [ed] Peter Fritzson, Hilding Elmqvist, Linköping, 2015, 671-679 p.Conference paper (Refereed)
    Abstract [en]

    The Modelica and FMI tool ecosystem is growing each year with new tools and methods becoming available. The open Modelica standard promises portability but it is important to ensure that a certain model behaves the same in different Modelica tools or in a different version of the same tool. It is also very important (for model evolution) to check that a new version of the same model produces comparable results. Finally, it is desirable to verify that a model exported in FMU form from a Modelica tool gives exactly the same results as the original model. This paper presents a framework for automatic regression testing as part of PySimulator which provides an efficient and concise way of testing if a model or a range of models behaves in the same way in several tools or versions of a tool by checking that the results produced are essentially identical. The FMI standard has been adopted by many tool vendors and is growing in popularity each year. This paper proposes a concept for building and simulating a system made from connected FMUs generated by different tools. The FMUs for Co-Simulation can be connected together using a GUI. The system model built graphically in this way can be saved for later use or simulated directly inside PySimulator. Active development is going on to support simulation of connected FMUs for Model Exchange.

  • 30.
    Asplund, Mikael
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Attitudes and Perceptions of IoT Security in Critical Societal Services2016In: IEEE Access, E-ISSN 2169-3536, Vol. 4, 2130-2138 p.Article in journal (Refereed)
    Abstract [en]

    A quiet revolution that impacts several sectors, ranging over transport, home automation, energy, industrial control, and health services is undergoing with addition of new networked devices leading to enhanced services. In this paper, we aim to identify information security requirements that are common over several (vertical) sectors, and in particular, ones that impact critical societal services, namely, the energy, water, and health management systems. We present the results of an interview-based study where actors in these sectors were asked about their perceptions and attitudes on the security of Internet of Things (IoT). We set these perceptions and attitudes in context through a literature review of IoT security, and relate to current challenges in this area. This paper demonstrates that despite an overall optimistic view on IoT in critical societal services, there is a lack of consensus on risks related to IoT security.

  • 31.
    Avdic, Kenan
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Melot, Nicolas
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Keller, Jörg
    FernUniversität in Hagen.
    Pipelined parallel sorting on the Intel SCC2011In: Fourth Swedish Workshop on Multi-Core Computing MCC-2011: November 23-25, 2011, Linköping University, Linköping, Sweden / [ed] Christoph Kessler, Linköping: Linköping University , 2011, Vol. S. 96-101, 96-101 p.Conference paper (Other academic)
    Abstract [en]

    The Single-Chip Cloud Computer (SCC) is an experimental processor created by Intel Labs. It comprises 48 Intel-IA32 cores linked by an on-chip high performance mesh network, as well as four DDR3 memory controllers to access an off-chip main memory. We investigate the adaptation of sorting onto SCC as an algorithm engineering problem. We argue that a combination of pipelined mergesort and sample sort will fit best to SCC's architecture. We also provide a mapping based on integer linear programming to address load balancing and latency considerations. We describe a prototype implementation of our proposai together with preliminary runtime measurements, that indicate the usefulness of this approach. As mergesort can be considered as a representative of the class of streaming applications, the techniques deveioped here should also apply to the other problems in this class, such as many applications for parallel embedded systems, i.e. MPSoC. 

  • 32.
    Avgouleas, Ioannis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    IoT Networking Resource Allocation and Cooperation2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Internet of Things (IoT) promises that "anything that can be connected, will be connected". It comprises of Information and Communication Technologies that interconnect billions of physical and visual things with some "basic" intelligence. The emerging IoT services will be able to react with minimal human intervention and further contribute to the big data era that requires real-time, ultrareliable, ubiquitous, scalable, and heterogeneous operation.

    This thesis is the result of our investigations on problems dealing with the evolution of such technologies. First, we explore the potential of using relay i.e., intermediate, nodes that assist users to transmit their packets in a a cellular network. Paper I provides insights into how adapting the cooperation of the relay's receiver and transmitter optimizes the network-wide throughput while the relay's queue stability is guaranteed.

    The next part of the thesis copes with the resource allocation of services on IoT devices equipped with multiple network interfaces. The resources are heterogeneous and can be split among dierent interfaces. Additionally, they are not interchangeable. In paper II, we develop optimization models for this resource allocation problem, prove the complexity of the models, and derive results that give intuition into the problems. Moreover, we propose algorithms that approximate the optimal solution and show under which circumstances this is possible.

    Finally, in paper III, we present a resource allocation problem specically for smart cities services. In comparison to the previous problem denition, resources are of one type but the IoT network device can oer capacities that vary over time. Furthermore, services have a tolerance regarding their preferred scheduling, namely, their allocation over time. We parametrize each service with a pricing function to indicate its tolerance to be served at the beginning of the scheduling window. We prove that the problem is computationally hard and provide numerical results to gain insight into how different pricing weight functions impact the allocations' distribution within the scheduling window.

    List of papers
    1. Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks
    Open this publication in new window or tab >>Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks
    2017 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 5, 7394-7404 p.Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we analyze the probabilistic cooperation of a full-duplex relay in a multiuser random-access network. The relay is equipped with on/off modes for the receiver and the transmitter independently. These modes are modeled as probabilities by which the receiver and the transmitter are activated. We provide analytical expressions for the performance of the relay queue, such as arrival and service rates, stability conditions, and the average queue size. We optimize the relays operation setup to maximize the network-wide throughput while, simultaneously, we keep the relays queue stable and lower the relays receptions and transmissions. Furthermore, we study the effect of the SINR threshold and the self-interference coefficient on the per-user and network-wide throughput. For low SINR threshold, we show under which circumstances it is beneficial to switch off the relay completely, or switch off the relays receiver only.

    Place, publisher, year, edition, pages
    IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017
    Keyword
    Cooperative communication; relays; relay networks; multiaccess communication; multiple access interference; internet of things (IoT); internet; wireless sensor networks (WSNs); body sensor networks (BSNs)
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-139423 (URN)10.1109/ACCESS.2016.2642540 (DOI)000403140800053 ()
    Note

    Funding Agencies|European Union [609094, 612361]

    Available from: 2017-08-07 Created: 2017-08-07 Last updated: 2017-08-21
    2. Allocation of Heterogeneous Resources of an IoT Device to Flexible Services
    Open this publication in new window or tab >>Allocation of Heterogeneous Resources of an IoT Device to Flexible Services
    Show others...
    2016 (English)In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 3, no 5, 691-700 p.Article in journal (Refereed) Published
    Abstract [en]

    Internet-of-Things (IoT) devices can be equipped with multiple heterogeneous network interfaces. An overwhelmingly large amount of services may demand some or all of these interfaces available resources. Herein, we present a precise mathematical formulation of assigning services to interfaces with heterogeneous resources in one or more rounds. For reasonable instance sizes, the presented formulation produces optimal solutions for this computationally hard problem. We prove the NP-completeness of the problem and develop two algorithms to approximate the optimal solution for big instance sizes. The first algorithm allocates the most demanding service requirements first, considering the average cost of interfaces resources. The second one calculates the demanding resource shares and allocates the most demanding of them first by choosing randomly among equally demanding shares. Finally, we provide simulation results giving insight into services splitting over different interfaces for both cases.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2016
    Keyword
    Internet of Things (IoT); mixed integer linear programming; network interfaces; optimization; resource management; scheduling algorithms
    National Category
    Communication Systems
    Identifiers
    urn:nbn:se:liu:diva-135000 (URN)10.1109/JIOT.2016.2535163 (DOI)000393047800006 ()
    Note

    Funding Agencies|Excellence Center at Linkoping-Lund in Information Technology; European Union [324515, 612316, 609094]

    Available from: 2017-03-06 Created: 2017-03-06 Last updated: 2017-08-21Bibliographically approved
  • 33.
    Avgouleas, Ioannis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks2017In: IEEE Access, E-ISSN 2169-3536, Vol. 5, 7394-7404 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyze the probabilistic cooperation of a full-duplex relay in a multiuser random-access network. The relay is equipped with on/off modes for the receiver and the transmitter independently. These modes are modeled as probabilities by which the receiver and the transmitter are activated. We provide analytical expressions for the performance of the relay queue, such as arrival and service rates, stability conditions, and the average queue size. We optimize the relays operation setup to maximize the network-wide throughput while, simultaneously, we keep the relays queue stable and lower the relays receptions and transmissions. Furthermore, we study the effect of the SINR threshold and the self-interference coefficient on the per-user and network-wide throughput. For low SINR threshold, we show under which circumstances it is beneficial to switch off the relay completely, or switch off the relays receiver only.

  • 34.
    Benjamin, Andersson
    Linköping University, Department of Computer and Information Science, Software and Systems.
    En teoretisk och praktisk jämförelse av alternativ till OpenLayers2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Med att de mobila enheterna blir allt mer kraftigare och webbtekniken går allt fortare framåt, så har webbapplikationer börjat blivit ett fullgott alternativ till vanliga nativeapplikationer. Presentera webbkartor med hjälp av ramverket OpenLayers har aldrig varit en större användarupplevelse på  mobil enhet då det är både stort och tungkört för en segare enhet. Samt att de aldrig var tänkte från början att fungera för  touchbaserade enheter, utan de är stöd som  senare har lagts på.

    Därför har jag hittat ett annat fullgott  alternativ till OpenLayers som heter Leaflet, som är anpassat att ha alla funktioner som  man kan kräva av en webbaserad karta och samtidigt fungera i mobila touch enheteter. Leaflet använder alla nya webbtekniker som HTML5 och CSS3 i största möjliga mån för att få sådan bra upplevelse som möjligt.

    Jag gjorde om hela klientdelen av en realtidskarta för blixtar i Leaflet istället, så att den skulle fungera bättre på en mobil enhet än vad den tidigare gjorde. Med denna implementation så visade sig att Leaflet kunde nå upp till alla krav som man kan ställa på en webbaserad karta. Resultatet blev en mycket lättare och snabbare klient med samma funktionalitet som den förra hade.

  • 35.
    Bergdahl, Otto
    et al.
    Linköping University, Department of Computer and Information Science.
    Granli, Petter
    Linköping University, Department of Computer and Information Science.
    Grimsdal, Gunnar
    Linköping University, Department of Computer and Information Science.
    Nilsson, Johan
    Linköping University, Department of Computer and Information Science.
    Arvidsson, Peter
    Linköping University, Department of Computer and Information Science.
    Bennich, Viktor
    Linköping University, Department of Computer and Information Science.
    Celik, Hakan
    Linköping University, Department of Computer and Information Science.
    Visual Care: Utveckling av en webbapplikation för att visualisera vårdprocesser2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report is about the production of the web application Visual Care. The product is a tool for visualising statistics provided by the customer Region Östergötland. The goal of the application is to help employees at Region Östergötland to plan treatment of cancer patients.

    The purpose of this report is to analyze the group's development process for the product. The product will not be used by the employees of Region Östergötland, but will instead be used as an inspiration for future projects by the customer. 

  • 36.
    Bergström, Anton
    et al.
    Linköping University, Department of Computer and Information Science.
    Dackner, Gustav
    Linköping University, Department of Computer and Information Science.
    Frank, Erik
    Linköping University, Department of Computer and Information Science.
    Olsson, Konrad
    Linköping University, Department of Computer and Information Science.
    Sjövall, Emil
    Linköping University, Department of Computer and Information Science.
    Sundqvist, Anton
    Linköping University, Department of Computer and Information Science.
    Wiksten, Elin
    Linköping University, Department of Computer and Information Science.
    Utveckling av webbapplikationen Folkbolaget: En e-handel med användbarhet i fokus2017Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    Microbreweries producing medium-strong beer are struggling to reach out to their customers. With the help of e-commerce, microbreweries can increase their interaction with their target market. E-commerce in Sweden is a growing trend, but in order to succeed with increased customer relations using a digital platform the end users need to feel a certain degree of satisfaction. A contributing factor to the satisfaction rate is that the end user experiences usability. This thesis discusses the results and development process of a useful e-commerce platform from a navigational, readability and responsiveness perspective. The thesis foundation is based on scientific research on usability in terms of navigability, readability and responsiveness. During development the Python and Flask frameworks were used for server operations and the clientside uses HTML, CSS and the Bootstrap framework. Furthermore, the JavaScript library jQuery was used for communication between front- and back-end. After the development phase an evaluation of the web application was conducted using usability testing. Based on presented theory and conducted tests the thesis conclusion states that the web application is useful. This is achieved by the user, regardless of where on the web application it is located, to navigate to the desired part of the web application with a maximum of three clicks. Furthermore, the choice of colour, text size and font is contributing to readability and finally, the use of CSS and Bootstraphas made the web application responsive.

  • 37.
    Berntsen, Eirik
    et al.
    University of Bergen, Norway.
    Babic, Ankica
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology. Univeristy of Bergen, Norway.
    Information System for Postmarket Surveillance of Total Joint Prostheses2015In: 16th Nordic-Baltic Conference on Biomedical Engineering / [ed] Henrik Mindedal ; Mikael Persson, Springer, 2015, 24-27 p.Conference paper (Refereed)
    Abstract [en]

    Storage, integration and presentation of clinical data is an important aspect of any modern medical research. The Biomaterials research group at the Haukeland University Hospital uses both their own locally generated clinical data and external registry data to examine explanted joint implants. As a solution to this challenge, a system prototype was developed that would enable further integration of these information systems into a multi-user environment.

    The system allows importing registry data and matching it with local data, viewing and editing of this information and exporting the integrated data for further statistical analysis. An evaluation consisting of both user testing and heuristic evaluation was carried out and generated constructive feedback.

    The prototype demonstrates the feasibility of combining these data sources in a single database and the future possibility of exposing parts of this information to external users through a web application.

    Future integration of external sources could improve the information management of biobank data for postmarket surveillance of medical devices.

  • 38.
    Birksjö, Marcus
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Event-based diagnostics in heavy-duty vehicles2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The integration of small computer units in vehicles has made new and more complex functionalitypossible within the vehicle industry. To verify that the functionality is working and to troubleshoot it when a fault is detected requires a set of diagnostic services. Due to the increasing complexity of the functionality the diagnostic services need to extract more data to be able to diagnose the functionality. This causes an increased network load which soon threatens to become too high for some of the current networks. New ways to diagnose functionality in vehicles are therefore needed.

    The aim of this thesis was to investigate the need for an event-based service within the domain of vehicle diagnostics as well as presenting a recommendation of how sucha service should be designed. The thesis also aimed at eliciting obstacles and pitfalls connected with the implementation of the service in the current software architecture in heavy duty vehicles.

    An industrial case study was performed at the Swedish company Scania to elicit the potential need, problems and limitations with an event-based service for vehicle diagnostics. First a set of experts representing different domains within vehicle diagnostics were interviewed to investigate the need and potential of the service for different use cases. Requirements were elicited and compared with the service ResponseOnEvent defined inthe ISO standard 14229-1:2013. A decision was then made to diverge from the standard inorder to increase the number of fulfilled requirements and flexibility of the service. A new proprietary service was therefore created and evaluated through a proof of concept wherea prototype of the service was implemented in one client and one server control unit. A final recommendation was then given suggesting how to implement an event-based service and how to solve the found problems.

    The elicitation of the need for an event-based service resulted a confirmed need in three different domains and 23 different requirements which the service ResponseOnEvent was compared against. The service failed to meet all the requirements and therefore a proprietary service was designed. The prototype implementation of the proprietary service showed on multiple difficulties connected to the realization of an event-based service in the current architecture. One of the biggest was the fact that diagnostic services was assumed to always have a one-to-one relation between request and response, which an event-based service would not have. Different workarounds were discovered and assessed. Another problem was the linking between an event triggered response message and the triggercondition. It was concluded that some restrictions would have to be made to facilitatethe process of linking a response to its trigger condition. Non-determinism was another problem, since there were no guarantees that an event would not trigger too often causinga bus overload. In the final recommendation there are suggestions of how to solve these problems and some suggested areas for further research.

    The thesis confirms the need for a new way to diagnose vehicle functionality due to their increased complexity and the limited bandwidth of some of today’s in-vehicle networks. The event-based service ResponseOnEvent offers a good alternative but might lacksome key functionality. Therefore it might be valuable to consider a proprietary service instead. Due to its nature, an event-based service might require a restructuring of thesystem architecture and limitations in the hardware might limit the usability and flexibilityof the service.

    Keywords: event-based service, Response on Event, ECU, Vehicle Diagnostics, UDS,KWP.

  • 39.
    Bjelkenstedt, Alf
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Web-Based Drawing Tool in GWT with Usability Testing and Usability Evaluation2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    On behalf of Inspectera HK AB in Norrköping a web-based drawing tool has been developed in Java, mainlywith the library Google Web Toolkit (GWT). The purpose of this tool is to facilitate both the staff's at Inspecteraand their client's work with different types of drawings such as blueprints for pest control, fire protection andespecially drawings of the company's e-service of self-checks. Besides developing the drawing tool usabilitytesting and a usability evaluation has been performed.

  • 40.
    Björck, Joel
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Ek, Johanna
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Ekberg, Isac
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Gunnarsson, Emil
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Lietha, Mikael
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Teneberg, Gustaf
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Wulfcrona, Mikael
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Öhrn, Rasmus
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Studentbåge: utvecklandet av en webbapplikation för cykelförsäljning2014Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [sv]

    Syftet med följande rapport är att beskriva erfarenheterna med designen och implementationen av en webbapplikation för e-handel. Arbetet genomfördes som en del av ett kandidatarbete, inom civilingenjörsprogrammet Industriell ekonomi vid Linköpings tekniska högskola, av ett team bestående av åtta studenter.

    Utgångspunkten för kandidatarbetet, som beskrivs i den här rapporten, var att teamet blev kontrakterat av en fiktiv kund (kursledningen) att skapa en handelsplats för cyklar. Då projektet bedrevs i utbildningssyfte hade kunden vissa krav på hur webbapplikationen skulle skapas både vad gäller slutgiltig funktionalitet och arbetsmetodik. Projektarbetet omfattade 18 högskolepoäng och sträckte sig över fem månader.

    Ur de specifikationer som kunden gav arbetade teamet fram en vision. Då cykeln är en integrerad del av studentlivet så beslutade teamet att skapa en handelsplats som de själva skulle vilja använda. Med utgångspunkt i teammedlemmarnas erfarenhet om cykelhandel i linköpingsområdet skapades konceptet Studentbåge med följande vision:

    ”Studentbåge; en köp- och säljplats för cyklar på nätet med låga barriärer för både köpare och säljare”

    Teamets erfarenheter som studenter var att cykelköp i stor utsträckning sker på andrahandsmarknaden men att det bland de befintliga tjänsterna saknades en aktör som erbjöd en tjänst som fokuserade på cyklar i närområdet. Teamets vision för en webbapplikation som uppfyllde det behovet inkluderade en rad funktioner för att fylla det uppfattade behovet. Möjligheten för användare att ladda upp cykelannonser var central då den tilltänkta affärsmodellen byggde på att användarna betalar för att lägga upp en annons. Då publicering av annonser och betalning av dessa kräver att användaruppgifter registreras så var även en inloggningsfunktion ett nödvändigt inslag i webbapplikationens design. För att användare skulle kunna hitta cyklar de var intresserade av så var även en sökfunktion del av visionen.

  • 41.
    Björnander, Daniel
    et al.
    Linköping University, Department of Computer and Information Science.
    Gezelius, Måns
    Linköping University, Department of Computer and Information Science.
    Gustafsson, Emil
    Linköping University, Department of Computer and Information Science.
    Leow, Raymond
    Linköping University, Department of Computer and Information Science.
    Lidstedt, Joakim
    Linköping University, Department of Computer and Information Science.
    Noring, Ludvig
    Linköping University, Department of Computer and Information Science.
    Petersson, Nils
    Linköping University, Department of Computer and Information Science.
    Pålsson, Jonatan
    Linköping University, Department of Computer and Information Science.
    Ångman, Mikael
    Linköping University, Department of Computer and Information Science.
    Utveckling inom Augmented Reality med Unity2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med den här rapporten är att behandla frågeställningar utifrån projektet, vars mål är att utveckla ett Augmented Reality-ramverk för att skapa värde för en kund, BioOptico.

    Punkter som programmeringsmiljön Unitys lämplighet vid utveckling av mobila AR-applikationer, hur BioVision kan implementeras så att det ger värde för BioOptico, vilka erfarenheter som kan dokumenteras efter arbetet med projektet och vilket stöd SEMAT Kernel ALPHA ger för det här projektet behandlas i den här rapporten.

    För att besvara dessa frågor används verktygen Unity och SEMAT Kernel ALPHA state cards under utvecklingen av BioVision. Genom agil utveckling och framtagning av tidiga prototyper undersöks vilka implementationssätt som ger värde för BioOptico och vilken dokumentation av erfarenheter som kan vara intressant för framtida projekt.

    Som resultat dokumenteras de områden där Unity lämpar sig väl för utveckling av mobila AR-applikationer, vilka de viktigaste beståndsdelarna var för hur BioVision implementerades så att det ger värde för BioOptico och vilka erfarenheter och vilket stöd som ges av utveckling av BioVision respektive användning av SEMAT Kernel ALPHA:s.

    Som slutsats ses Unity som en lämplig utvecklingsmiljö för utveckling av AR-applikationer, medan SEMAT Kernel ALPHA kan vara användbart, dock överflödigt, vid utveckling av BioVision. De viktigaste lärdomarna att ta med sig från projektet är att planera, utveckla och dokumentera i god tid. Slutligen dras slutsatsen om att strukturen på projektet och inte bara produkten som skapas spelar en stor roll för hur applikationen kan ge värde för BioOptico.

  • 42.
    Blagojevic, Nebojsa
    et al.
    Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology.
    Bohlers, Johanna
    Linköping University, Department of Management and Engineering. Linköping University, The Institute of Technology.
    Realisering av affärssytemets nytoeffekter: En studie om påverkansfaktorer under postimplementeringen2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Det finns många fördelar att hämta ur ett affärssystem, men både vid den initiala implementeringen och den fortsatta utvecklingen av ett företags affärssystem uppkommer problem. För att realisera fördelar i så stor grad som möjligt krävs det att företag agerar på ett fördelaktigt sätt för att överkomma hindrena. Tidigare forskning har behandlat hur företag bör agera under den initiala implementeringen medan denna rapports syfte är att identifiera viktiga områden som påverkar företags möjligheter att realiserat ytterligare fördelar under det fortsatta utvecklingen av affärssystemet, så kallat postimplementeringen.

    Med hjälp av en litteraturstudie, innefattande affärssystemets livscykel, nyttoeffekter och kritiska områden för realiseringen av nyttoeffekter vid implementering av affärssystem, samt en intervjustudie med totalt elva företag och en implementeringskonsult, där två företag intervjuades djupare, har slutsatser dragits. Resultatet tyder på att det ramverk för kritiska påverkansfaktorer som är presenterade i litteraturen och gäller hela affärssystemets livscykel i stora drag även är tillämpbart på postimplementeringsfasen. Däremot har det identifierats ett par områden, ej specifikt behandlade i litteraturen, som anses har en påverkan på hur väl företag lyckas med att hantera de kritiska dimensionerna: dessa är intressenternas förhandlingskraft och företagets storlek.

    Utifrån denna analys har dimensionerna ledning och organisation benämnts till förutsättare och dimensionerna projekt och system till förenklare, där de förutsättande dimensionerna anses ha större påverkande kraft på realiseringen av nyttoeffekter under postimplementeringen. De förenklande dimensionerna däremot kräver en avvägning mellan resurser och nytta från företagets sida. Denna avvägning är beroende av den företagsspecifika situationen samt företagets förmåga att hantera de förutsättande dimensionerna. 

  • 43.
    Blomkvist, Johan
    et al.
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Clatworthy, Simon
    Linköping University.
    Holmlid, Stefan
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Ways of seeing the design material of service2016In: Service Design Geographies. Proceedings of the ServDes.2016 Conference / [ed] Nicola Morelli, Amalia de Götzen, Francesco Grani, Linköping: Linköping University Electronic Press, 2016, Vol. 125, 1-13 p.Conference paper (Refereed)
    Abstract [en]

    This paper makes a contribution to the current conceptualisation of service as a design material from three different perspectives. We use definitions of the term material, the connection with service logic and the techniques that service designers use to discuss ways to understand service from a design perspective. Service designers have tools for working with components, things, locations, actions, procedures, interactions and experiences at their disposal. Service designers work with a meta-material for the most part, which is a material representation of the services they are (re-)designing. Unlike fields where the material is worked into a finished form, the material of service design traverses between the concrete and the abstract throughout the design process.

  • 44.
    Blomkvist, Johan
    et al.
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Fjuk, Annita
    Linköping University.
    Sayapina, Vasilisa
    Linköping University.
    Low threshold service design: desktop walkthrough2016In: Service design geographies: Proceedings of the ServDes.2016 Conference / [ed] Nicola Morelli, Amalia de Götzen, Francesco Grani, Linköping: Linköping University Electronic Press, 2016, 154-166 p.Conference paper (Refereed)
    Abstract [en]

    This paper introduces the first academic characterisation of the desktop walkthrough technique. Desktop walkthrough is considered here as a service design technique using a collaboratively built miniature environment to construct knowledge about a specific service. It is further examined as a technique for rapidly exploring and designing a service concept. The analytical lens of the paper is outlined from socio-cultural theories on human development where any human action is developed from, and emulated by, social interactions and the intellectual and physical artefacts herein. The analysis shows that desktop walkthrough enabled teams to design a holistic service journey with low threshold usage, and provided a means for exploring and designing the complexity of customer journeys and the backstage organizational processes.

  • 45.
    Blomkvist, Johan
    et al.
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Overkamp, Tim
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Holmlid, Stefan
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Research in the first four service design and innovation (ServDes) conferences2016In: Service design geographies: Proceedings of the ServDes.2016 Conference / [ed] Nicola Morelli, Amalia de Götzen, Francesco Grani, Linköping: Linköping University Electronic Press, 2016, 167-179 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we take a closer look at the papers published during the first four Service design and innovation (ServDes) conferences and sources that the authors of those papers have referenced. The analysis uses the academic search engine Scopus and the references found in the conferences’ Proceedings. In total 206 authors have contributed to the 105 research papers presented at ServDes, and 53% of all ServDes papers have been referenced at a later ServDes. ServDes authors are informed by research published mainly after 1999 (79,2%), primarily within the fields of Business, Computer Science and Engineering. We also look at what authors publish their research at ServDes and the percentage of self-referencing (27%) as well as within-conference referencing (2,4% of references) to examine the progression within the field through the research published at ServDes.

  • 46.
    Bock, Alexander
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Mays, M. Leila
    NASA Goddard Space Flight Center, Greenbelt, MD, USA.
    Rastaetter, Lutz
    NASA Goddard Space Flight Center, Greenbelt, MD, USA.
    Ynnerman, Anders
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ropinski, Timo
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    VCMass: A Framework for Verification of Coronal Mass Ejection Ensemble Simulations2014Conference paper (Refereed)
    Abstract [en]

    Supporting the growing field of space weather forecasting, we propose a framework to analyze ensemble simulations of coronal mass ejections. As the current simulation technique requires manual input, uncertainty is introduced into the simulation pipeline which leads to inaccurate predictions. Using our system, the analyst can compare ensemble members against ground truth data (arrival time and geo-effectivity) as well as information derived from satellite imagery. The simulations can be compared on a global basis, based on time-resolved quality measures, and as a 3D volumetric rendering with embedded satellite imagery in a multi-view setup. This flexible framework provides the expert with the tools to increase the knowledge about the, as of yet not fully understood, principles behind the formation of coronal mass ejections.

  • 47.
    Bodirsky, Manuel
    et al.
    Technical University of Dresden, Germany.
    Jonsson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    A Model-Theoretic View on Qualitative Constraint Reasoning2017In: The journal of artificial intelligence research, ISSN 1076-9757, E-ISSN 1943-5037, Vol. 58, 339-385 p.Article in journal (Refereed)
    Abstract [en]

    Qualitative reasoning formalisms are an active research topic in artificial intelligence. In this survey we present a model-theoretic perspective on qualitative constraint reasoning and explain some of the basic concepts and results in an accessible way. In particular, we discuss the significance of omega-categoricity for qualitative reasoning, of primitive positive interpretations for complexity analysis, and of Datalog as a unifying language for describing local consistency algorithms.

  • 48.
    Boije, Niklas
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Borg, Kristoffer
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Semi-automatic code-to-code transformer for Java: Transformation of library calls2016Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
    Abstract [en]

    Having the ability to perform large automatic software changes in a code base gives new possibilities for software restructuring and cost savings. The possibility of replacing software libraries in a semi-automatic way has been studied. String metrics are used to find equivalents between two libraries by looking at class- and method names. Rules based on the equivalents are then used to describe how to apply the transformation to the code base. Using the abstract syntax tree, locations for replacements are found and transformations are performed. After the transformations have been performed, an evaluation of the saved effort of doing the replacement automatically versus manually is made. It shows that a large part of the cost can be saved. An additional evaluation calculating the maintenance cost saved annually by changing libraries is also performed in order to prove the claim that an exchange can reduce the annual cost for the project.

  • 49.
    Bolin, Mårten
    et al.
    Linköping University, Department of Computer and Information Science.
    Dietmann, Andreas
    Linköping University, Department of Computer and Information Science.
    Granat, Elvin
    Linköping University, Department of Computer and Information Science.
    Jönsson, Emelie
    Linköping University, Department of Computer and Information Science.
    Modigh, Edvin
    Linköping University, Department of Computer and Information Science.
    Olausson, Erik
    Linköping University, Department of Computer and Information Science.
    Pettersson, Ellinor
    Linköping University, Department of Computer and Information Science.
    Sidén, Erik
    Linköping University, Department of Computer and Information Science.
    Att utveckla en trovärdig och användbar webbapplikation: Spacefinder - Framtagning av en webbapplikation för uthyrning av förråd och andra förvaringsutrymmen.2017Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    The purpose of this report is to develop a web application to support the current issue, with the aid of theory and practical knowledge, "How should an e-store for ad slots be designed to gain confidence in the visitors and be useful with regard to navigability, relevance of content And readability?". A literature study was conducted and theory compiled to provide a basis for development. The process followed relevant theories and the web application was built with modern technological solutions. The final product provides relevant features and applications, which were then tested by a number of external testers, after which a survey could be answered. Based on this data, it could then be concluded that the web application complied with the requirements that are fundamentally considered to be a useful, navigable and credible web application. The original question can thus be answered with this report's theory, method and implementation.

  • 50.
    Bordoloi, Unmesh
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, The Institute of Technology.
    Rezine, Ahmed
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, The Institute of Technology.
    Software Model Checking for GPGPU Programs, Towards a Verification Tool2011Report (Other academic)
    Abstract [en]

    The tremendous computing power GPUs are capable of makes of them the epicenter of an unprecedented attention for applications other than graphics and gaming. Apart from the highly parallel nature of the programs to be run on GPUs, the sought after gain in computing power is only achieved with low level tuning at threads level and is therefore veryerror prone. In fact the level of intricacy involved when writing such programs is already a problem and will become a major bottleneck in spreading the technology.

    Only very recent and rare works started looking into using formal methods for helping GPU programmers avoiding errors like data races, incorrect synchronizations or assertions violations. These are at their infancy and directly import techniques adapted for other (sequential) systems with simple approximations for concurrency. Besides that, theonly help we are aware of right now takes a concrete input and explores a tiny portion of the possible thread scheduling looking for such errors. This easily misses common errors and makes of GPU programming a nightmare task. There is therefore still a lot of work to do in order to come up with helpful and scalable tools for today's and tomorrow's GPGPU software.

    We state in this paper our intention in building in Linköping a agship verication tool that will take CUDA code and track and report, with minimal assistance from the programmer, errors like data races, incorrect synchronizations or assertions violations. In order to achieve this ambitious and vital goal for the widespread of GPU programming, webuild on our experience using and implementing CUDA and GPU code and on our latest work in the verication of multicore and concurrent programs. In fact, GPU programs like those written in CUDA are suitable for verication as they typically neither manipulate pointer arithmetics nor allowrecursion. This restricts the focus to concurrency and array manipulation, combined with intra and inter procedural analysis. To give a avor of where we start from, we report on our experiments in automatically verifying two synchronization algorithms that appeared in a recent paper proposing effiient barriers for inter-block synchronization. Unlike any other verication approach for GPU programs,we can show that the algorithms neither deadlock nor violate the barrier condition regardless of the number of threads. We also capture bugs in case basic relations are violated between the number of blocks and the number of threads per block.

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