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  • 201.
    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.

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  • 202.
    Alegroth, Emil
    et al.
    Blekinge Inst Technol, Sweden.
    Borch Petersen, Eline
    Linköping University, Department of Clinical and Experimental Medicine, Division of Speech language pathology, Audiology and Otorhinolaryngology. Linköping University, Faculty of Medicine and Health Sciences.
    Tinnerholm, John
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    A Failed attempt at creating Guidelines for Visual GUI Testing: An industrial case study2021In: 2021 14TH IEEE CONFERENCE ON SOFTWARE TESTING, VERIFICATION AND VALIDATION (ICST 2021), IEEE COMPUTER SOC , 2021, p. 340-350Conference paper (Refereed)
    Abstract [en]

    Software development is governed by guidelines that aim to improve the codes qualities, such as maintainability. However, whilst coding guidelines are commonplace for software, guidelines for testware are much less common. In particular, for GUI-based tests driven with image recognition, also referred to as Visual GUI Testing (VGT), explicit coding guidelines are missing. In this industrial case study, performed at the Swedish defence contractor Saab AB, we propose a set of coding guidelines for VGT and evaluate their impact on test scripts for an industrial, safety-critical system. To study the guidelines effect on maintenance costs, five representative manual test cases are each translated with and without the proposed guidelines in the two VGT tools SikuliX and EyeAutomate. As such, 20 test scripts were developed, with a combined development cost of more than 100 man-hours. Three of the tests are then maintained by one researcher and two practitioners for another version of the system and costs measured to evaluate return on investment. This analysis is complemented with observations and interviews to elicit practitioners perceptions and experiences with VGT. Results show that scripts developed with the guidelines had higher maintenance costs than scripts developed without guide-lines. This is supported by qualitative results that many of the guidelines are considered inappropriate, superfluous or unnecessary due to the inherent properties of the scripts, e.g. their natural small size, linear flows, natural separation of concerns, and more. We conclude that there are differences between VGT scripts and software that prohibit direct translation of guidelines between the two. As such, we consider our study as a failure but argue that several lessons can be drawn from our results to guide future research into guidelines for VGT and GUI-based test automation.

  • 203.
    Alenljung, Beatrice
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Decision-making in the requirements engineering process: a human-centered approach2005Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Complex decision-making is a prominent aspect of requirements engineering and the need for improved decision support for requirements engineers has been identified by a number of authors. A first step toward better decision support in requirements engineering is to understand decision-makers- complex decision situations. To gain a holistic perspective of the decision situation from a decision-makers perspective, a decision situation framework has been created. The framework evolved through a literature analysis of decision support systems and decision-making theories. The decision situation of requirements engineers has been studied at Ericsson Microwave Systems and is described in this thesis. Aspects of decision situations are decision matters, decision-making activities, and decision processes. Another aspect of decision situations is the factors that affect the decision-maker. A number of interrelated factors have been identified. Each factor consists of problems and these are related to decision-making theories. The consequences of this for requirements engineering decision support, represented as a list that consists of desirable high-level characteristics, are also discussed.

  • 204. Order onlineBuy this publication >>
    Alenljung, Beatrice
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Envisioning a Future Decision Support System for Requirements Engineering: A Holistic and Human-centred Perspective2008Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Complex decision-making is a prominent aspect of requirements engineering (RE) and the need for improved decision support for RE decision-makers has been identified by a number of authors in the research literature. The fundamental viewpoint that permeates this thesis is that RE decision-making can be substantially improved by RE decision support systems (REDSS) based on the actual needs of RE decision-makers as well as the actual generic human decision-making activities that take place in the RE decision processes. Thus, a first step toward better decision support in requirements engineering is to understand complex decision situations of decision-makers. In order to gain a holistic view of the decision situation from a decision-maker’s perspective, a decision situation framework has been created. The framework evolved through an analysis of decision support systems literature and decision-making theories. The decision situation of RE decision-makers has been studied at a systems engineering company and is depicted in this thesis. These situations are described in terms of, for example, RE decision matters, RE decision-making activities, and RE decision processes. Factors that affect RE decision-makers are also identified. Each factor consists of problems and difficulties. Based on the empirical findings, a number of desirable characteristics of a visionary REDSS are suggested. Examples of characteristics are to reduce the cognitive load, to support creativity and idea generation, and to support decision communication. One or more guiding principles are proposed for each characteristic and available techniques are described. The purpose of the principles and techniques is to direct further efforts concerning how to find a solution that can fulfil the characteristic. Our contributions are intended to serve as a road map that can direct the efforts of researchers addressing RE decision-making and RE decision support problems. Our intention is to widen the scope and provide new lines of thought about how decision-making in RE can be supported and improved.

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  • 205.
    Alenljung, Zackarias
    Linköping University, Department of Computer and Information Science.
    Augmented Reality and Remote Interaction with Military Unmanned Ground Vehicles2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Interaction with unmanned ground vehicles have traditionally been done through a lap-top based system. New technology is on the rise which can provide new benefits to operating soldiers, with superimposed information and a more lightweight control unit, namely augmented reality. Designing interfaces for augmented reality systems have seen an improvement but has yet to be widely implemented in various domains. Satisfaction and high user acceptance are aspects that have been identified to be factors for success in the field of human-robot interaction. This thesis intends to explore interface design solutions for interactions with unmanned ground vehicles through augmented reality in head-mounted displays. This has been done through an iterative design process in the form of concept generation and prototyping. The produced prototype has then been evaluated with users to find usability issues and to measure the potential in the prototype to be satisfactory and have a high user acceptance. The evaluation resulted in eight usability issues of which three was critical. The three usability issues are (1) Video module was placed too far down of the user’s view, (2) Difficulties to find modules outside of the view, and (3) Crucial information to distinguish units was non-existent. The prototype did show signs of having potential of being satisfactory and have a high user acceptance, although there are issues which still need to be resolved before this user interface could be used by the military. It is a first step towards integrating augmented reality as a tool when interacting with UGV.

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  • 206.
    Alenlöv, Johan
    et al.
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning. Linköping University, Faculty of Science & Engineering.
    Doucet, Arnaud
    Univ Oxford, England.
    Lindsten, Fredrik
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning. Linköping University, Faculty of Science & Engineering.
    Pseudo-Marginal Hamiltonian Monte Carlo2021In: Journal of machine learning research, ISSN 1532-4435, E-ISSN 1533-7928, Vol. 22Article in journal (Refereed)
    Abstract [en]

    Bayesian inference in the presence of an intractable likelihood function is computationally challenging. When following a Markov chain Monte Carlo (MCMC) approach to approximate the posterior distribution in this context, one typically either uses MCMC schemes which target the joint posterior of the parameters and some auxiliary latent variables, or pseudo-marginal Metropolis-Hastings (MH) schemes. The latter mimic a MH algorithm targeting the marginal posterior of the parameters by approximating unbiasedly the intractable likelihood. However, in scenarios where the parameters and auxiliary variables are strongly correlated under the posterior and/or this posterior is multimodal, Gibbs sampling or Hamiltonian Monte Carlo (HMC) will perform poorly and the pseudo-marginal MH algorithm, as any other MH scheme, will be inefficient for high-dimensional parameters. We propose here an original MCMC algorithm, termed pseudo-marginal HMC, which combines the advantages of both HMC and pseudo-marginal schemes. Specifically, the PM-HMC method is controlled by a precision parameter N, controlling the approximation of the likelihood and, for any N, it samples the marginal posterior of the parameters. Additionally, as N tends to infinity, its sample trajectories and acceptance probability converge to those of an ideal, but intractable, HMC algorithm which would have access to the intractable likelihood and its gradient. We demonstrate through experiments that PM-HMC can outperform significantly both standard HMC and pseudo-marginal MH schemes.

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  • 207.
    Alesand, Alexander
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Emulating 3G Network Characteristics on WiFi Networks2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mobile applications should work regardless of which type of wireless interface is used, and should be able to conceal unstable connections from the user to improve user experience. Therefore, network testing is important when developing mobile applications, but it is a challenge to reproduce network conditions when using real cellular networks since the test engineer has no control over the quality of the cellular network. Existing software tools can restrict bandwidth and add latency to the connection, but these tools do not accurately emulate cellular networks.

    This thesis proposes a system where it is possible to shape the network traffic for connected devices to mimic the network patterns of a real cellular connection when running on a WiFi connection. The design presented in this thesis is intended for testing mobile applications under diverse 3G connection parameters, such as latency, bandwidth and other characteristics.

    This thesis was conducted at Spotify, a company that provides a music streaming service which is a frequent user of network data traffic. The 3G emulator was evaluated using the Spotify Android application by measuring the correlation between packet traces from a real 3G connection and the 3G emulator. This correlation was compared to the correlation between packet traces from a real 3G connection and the current network emulator at Spotify. The evaluation shows that the proposed 3G emulator outperforms the current network emulator when performing tests on the Spotify application for Android. By using this emulator, we expect the network testing to become more effective as any 3G condition can be tested with repeatable results.

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    Alesand - Emulating 3G Network Characteristics on WiFi Networks
  • 208.
    Alesand, Alexander
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Vergara, Ekhiotz Jon
    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.
    Communication Energy Evaluation for Mobile Applications: Emulating 3G over WiFi2016In: ProceedingENERGY-SIM '16 Proceedings of the 2nd International Workshop on Energy-Aware Simulation, ACM Digital Library, 2016Conference paper (Refereed)
    Abstract [en]

    Ubiquitous connectivity and massive use of mobile applications are currently hampered by fast battery drain of mobile devices. The communication energy of a mobile device is highly inuenced by the cellular operator conguration and the communication data pattern. Although testing the functionality and eciency of an application under diverse and realistic network settings is desirable, it is currently limited at the application developer test environment. It is generally hard to mimic di erent operator (infrastructure) settings that impact battery drain. In this paper we propose a system that creates a realistic cellular network testing environment for mobile applications on top of a WiFi network. A mobile device connects via WiFi to an emulator which shapes the uplink and downlink WiFi trac using real cellular operator conguration parameters. The system provides higher test repeatability compared to live networks and can be congured to emulate diverse cellular network parameters. These parameters, which determine the energy consumption, can be changed modularly and eciently. The evaluation of the resulting trac of the emulator compared to real cellular packet races from a streaming application shows a high correlation (0.97-0.98). The work has resulted in integration of the emulator within Spotify's test environment.

  • 209.
    Alesand, Elias
    et al.
    Linköping University, Department of Computer and Information Science.
    Sterneling, Hanna
    Linköping University, Department of Computer and Information Science.
    A shoulder-surfing resistant graphical password system2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The focus of this report is to discuss graphical password systems and how they can contribute to handle security problems that threaten authentication processes. One such threat is shoulder-surfing attacks, which are also reviewed in this report. Three already existing systems that are claimed to be shoulder-surfing resilient are described and a new proposed system is presented and evaluated through a user study. Moreover, the system is compared to the mentioned existing systems to further evaluate the usability, memorability and the time it takes to authenticate. The user study shows that test subjects are able to remember their chosen password one week after having registered and signed in once. It is also shown that the average time to sign in to the system after five minutes of practice is within a range of 3.30 to 5.70 seconds. The participants in the experiments gave the system an average score above 68 on the System Usability Scale, which is the score of an average system.

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  • 210.
    Alexandersson, Henrik
    et al.
    Linköping University, Department of Computer and Information Science.
    Bouganim, Jakob
    Linköping University, Department of Computer and Information Science.
    Do Ruibin, Kevin
    Linköping University, Department of Computer and Information Science.
    Gunnarsson, Daniel
    Linköping University, Department of Computer and Information Science.
    Hyllienmark, Erik
    Linköping University, Department of Computer and Information Science.
    Karlsson, Anton
    Linköping University, Department of Computer and Information Science.
    Nathanaelsson, Sara
    Linköping University, Department of Computer and Information Science.
    Ringqvist, Hugo
    Linköping University, Department of Computer and Information Science.
    En studie kring utvecklingen av webbapplikationen HappyBox2017Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    The purpose of the report was to examine how an online store selling dinner kits could be designed and implemented to be usable in reference to navigability while inducing trust and encouraging customer engagement. A pre-study was used to determine the interest for the product among the target audience. Thenceforth a prototype was developed and the design of the web application was formed. An iterative process was used during the development of the application and through usability testing the elements of the scientific question was evaluated. The report presents and discusses the design of the web application and how it has been used to fulfill the purpose of the report. Technical solutions regarding the modeling of the web application are discussed and motivated. Finally, it is argued that feedback and distinct buttons make the application trustworthy and easy to navigate over. Conclusions about customer engagement were difficult to make.

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  • 211.
    Alexandersson, Joel
    et al.
    Linköping University, Department of Computer and Information Science.
    Choura, Lucia
    Linköping University, Department of Computer and Information Science.
    Enhancing Usability in Aerospace Software Development Processes Through Gamification2024Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis explores the integration of gamification into the Software Development Process (SDP) at Saab, a defense and aerospace company. The thesis aims to address some of the complexities of the SDP standard used in the industry, DO-178C. The research primarily focuses on how gamification principles can enhance the usability of software development processes in aerospace. The method includes a pre-study, an inception phase, and two sprints, where a gamified tool is designed, implemented, and revised based on feedback from developers at Saab. The results of interviews after these sprints, along with insights from the inception phase, are discussed to evaluate the effectiveness and impact of the gamified tool. 

    The findings indicate that gamification can make the SDP more approachable and engaging for developers, with elements like real-time progress tracking, quizzes, and certificates being well-received. However, the effectiveness of these gamification elements varies among individuals, underscoring the importance of tailoring these elements to user preferences and the specific context of aerospace software development.

    This research contributes to the understanding of gamification's role in improving SDP usability in the aerospace industry, highlighting the need for careful customization of gamification to individuals and the context. Although the study provides valuable insights, it also acknowledges limitations, including the hypothetical nature of the gamified tool used and the reliance on user feedback, suggesting future research should involve more practical implementations and a focus on long-term impacts on productivity and user satisfaction.

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  • 212.
    Alfredson, Jens
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering. Saab Aeronaut, S-58247 Linkoping, Sweden.
    Adaptive Interaction Criteria for Future Remotely Piloted Aircraft2017In: ADVANCES IN HUMAN FACTORS IN ROBOTS AND UNMANNED SYSTEMS, SPRINGER INT PUBLISHING AG , 2017, Vol. 499, p. 281-289Conference paper (Refereed)
    Abstract [en]

    There are technical trends and operational needs within the aviation domain towards adaptive behavior. This study focus on adaptive interaction criteria for future remotely piloted aircraft. Criteria that could be used to guide and evaluate design as well as to create a model for adaptive interaction used by autonomous functions and decision support. A scenario and guidelines from the literature, used as example criteria, was presented in a questionnaire to participants from academia/researchers, end users, and aircraft development engineers. Several guidelines had a wide acceptance among the participants, but there was also aspects missing for the application of supporting adaptive interaction for remotely piloted aircraft. The various groups of participants contributed by different aspects supports the idea of having various stakeholders contributing with complementary views. Aspects that the participants found missing includes, predictability, aviation domain specifics, risk analysis, complexity and how people perceive autonomy and attribute intentions.

  • 213.
    Alfredson, Jens
    et al.
    SAAB, Linköping, Sweden.
    Johansson, Björn
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Arts and Sciences.
    Gonzaga Trabasso, Luis
    Aeronautics Institute of Technology, Brazil.
    Schminder, Jörg
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Granlund, Rego
    Research Institutes of Sweden SICS East, Linköping, Sweden.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    DESIGN OF A DISTRIBUTED HUMAN FACTORS LABORATORY FOR FUTURE AIRSYSTEMS2018In: ICAS congress proceeding, International Council of the Aeronautical Sciences , 2018, article id ICAS2018_0305Conference paper (Other academic)
    Abstract [en]

    This paper presents a rationale for structuring a distributed human factors laboratory for future air systems. The distributed herein refers to two aspects: content and geographic. As for content, the laboratory is structured in two levels, namely, individual, and team. As for geographic, the laboratory infrastructure is distributed in three physically separate facilities, namely, Department of Computer and Information Science (IDA) and Department of Management and Engineering (IEI) from Linköping University – Sweden and the Competence Center in Manufacturing from the Aeronautics Institute of Technology (ITA) – Brazil.

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  • 214.
    Alfredson, Jens
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering. Saab Aeronaut, Linkoping, Sweden.
    Trabasso, Luís Gonzaga
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering. ITA, Brazil.
    Blomstrand, Niklas
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Eckerberg, Maria
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Klamer, Linda
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Ledin, Johanna
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Tarander, Jasmine
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Bång, Magnus
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Engine Failure Induced Task Load Transient for Simulation Based Certification Aiding for Aircraft2018In: ADVANCES IN HUMAN ASPECTS OF TRANSPORTATION, SPRINGER INTERNATIONAL PUBLISHING AG , 2018, Vol. 597, p. 79-86Conference paper (Refereed)
    Abstract [en]

    This study is one of a series of studies, researching various aspects that all aim at enhanced simulation based certification aiding for aircraft. An experimental within-group design study was performed with 10 participants ( 5 male, and 5 female). The results showed a significant difference, F(2,16) = 5.11, p = 0.019, in mental workload between an engine failure condition and an normal condition for eye blink frequency. No effect of speed at the engine failure event on mental workload was found.

  • 215.
    Alfredsson, Marcus
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Lundmark, Eric
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Workflow graph editing and visualization in HTML5 and Javascript2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Being able to run applications written in a single language on multiple platforms is a strong incentive for migrating applications to the web. This along with the possibility to avoid the sometimes problematic procedure of installing software, makes the case even stronger. This thesis investigates how to migrate a workflow graph editing system into a web technology in order to publish it on the web. We will evaluate a number of different technologies such as WebGL, HTML5 canvas and SVG. SVG is deemed as the preferred technology due to its advantages when it comes to interaction. As it can leverage JavaScripts event system we get a potent way of handling events without writing a single line of code. When combining this with the framework D3JS we achieve a great tool for writing workflow management systems.

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  • 216.
    Algergawy, Alsayed
    et al.
    Friedrich Schiller University Jena, Germany.
    Cheatham, Michelle
    Wright State University, USA.
    Faria, Daniel
    Instituto Gulbenkian de Ciencia, Lisbon, Portugal.
    Ferrara, Alfio
    Universita degli studi di Milano, Italy.
    Fundulaki, Irina
    FORTH, Greece.
    Harrow, Ian
    Pistoia Alliance Inc., USA.
    Hertling, Sven
    University of Mannheim, Germany.
    Jimenez-Ruiz, Ernesto
    Alan Turing Institute, London, UK; University of Oslo, Norway.
    Karam, Naouel
    Fraunhofer FOKUS, Berlin, Germany.
    Khiat, Abderrahman
    Freie Universität Berlin, Germany.
    Lambrix, Patrick
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Li, Huanyu
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Montanelli, Stefano
    Universita degli studi di Milano, Italy.
    Paulheim, Heiko
    University of Mannheim, Germany.
    Pesquita, Catia
    Universidade de Lisboa, Portugal.
    Saveta, Tzanina
    FORTH, Greece.
    Schmidt, Daniela
    Pontifical Catholic University of Rio Grande do Sul, Brazil.
    Shvaiko, Pavel
    Trentino Digitale SpA, Trento, Italy.
    Splendiani, Andrea
    Pistoia Alliance Inc., USA.
    Thiéblin, Elodie
    IRIT, France; Université Toulouse II, Toulouse, France.
    Trojahn, Cassia
    IRIT, France; Université Toulouse II, Toulouse, France.
    Vatascinova, Jana
    University of Economics, Prague, Czech Republic.
    Zamazal, Ondrej
    University of Economics, Prague, Czech Republic.
    Zhou, Lu
    Wright State University, USA.
    Results of the Ontology Alignment Evaluation Initiative 20182018In: Proceedings of the 13th International Workshop on Ontology Matching: co-located with the 17th International Semantic Web Conference (ISWC 2018) / [ed] Pavel Shvaiko, Jérôme Euzenat, Ernesto Jiménez-Ruiz, Michelle Cheatham, Oktie Hassanzadeh, Aachen, Germany: CEUR Workshop Proceedings , 2018, Vol. 2288, p. 76-116Conference paper (Refereed)
    Abstract [en]

    The Ontology Alignment Evaluation Initiative (OAEI) aims at comparing ontology matching systems on precisely defined test cases. These test cases can be based on ontologies of different levels of complexity (from simple thesauri to expressive OWL ontologies) and use different evaluation modalities (e.g., blind evaluation, open evaluation, or consensus). The OAEI 2018 campaign offered 12 tracks with 23 test cases, and was attended by 19 participants. This paper is an overall presentation of that campaign.

  • 217.
    Algergawy, Alsayed
    et al.
    Friedrich Schiller University Jena, Germany .
    Faria, Daniel
    BioData.pt, INESC-ID, Lisbon, Portugal .
    Ferrara, Alfio
    Universita degli studi di Milano, Italy .
    Fundulaki, Irini
    Institute of Computer Science-FORTH, Heraklion, Greece .
    Harrow, Ian
    Pistoia Alliance Inc., USA .
    Hertling, Sven
    University of Mannheim, Germany .
    Jimenez-Ruiz, Ernesto
    City University of London, UK and University of Oslo, Norway .
    Karam, Naouel
    Fraunhofer FOKUS, Berlin, Germany .
    Khiat, Abderrahmane
    Fraunhofer IAIS, Sankt Augustin, Bonn, Germany.
    Lambrix, Patrick
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    Li, Huanyu
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Montanelli, Stefano
    Universita degli studi di Milano, Italy .
    Paulheim, Heiko
    University of Mannheim, Germany.
    Pesquita, Catia
    LASIGE, Faculdade de Ciencias, Universidade de Lisboa, Portugal .
    Saveta, Tzanina
    Institute of Computer Science-FORTH, Heraklion, Greece .
    Shvaiko, Pavel
    TasLab, Trentino Digitale SpA, Trento, Italy .
    Splendiani, Andrea
    Pistoia Alliance Inc., USA.
    Thieblin, Elodie
    IRIT & Universite Toulouse II, Toulouse, France .
    Trojahn, Cassia
    IRIT & Universite Toulouse II, Toulouse, France .
    Vatascinova, Jana
    University of Economics, Prague, Czech Republic .
    Zamazal, Ondrej
    University of Economics, Prague, Czech Republic .
    Zhou, Lu
    Kansas State University, USA .
    Results of the Ontology Alignment Evaluation Initiative 20192019In: Proceedings of the 14th International Workshop on Ontology Matchingco-located with the 18th International Semantic Web Conference (ISWC 2019) / [ed] Pavel Shvaiko, Jérôme Euzenat, Ernesto Jiménez-Ruiz, Oktie Hassanzadeh, Cássia Trojahn,, Aachen: CEUR Workshop Proceedings , 2019, p. 46-85Conference paper (Refereed)
    Abstract [en]

    The Ontology Alignment Evaluation Initiative (OAEI) aims at comparing ontology matching systems on precisely defined test cases. These test cases can be based on ontologies of different levels of complexity (from simple thesauri to expressive OWL ontologies) and use different evaluation modalities (e.g., blind evaluation,open evaluation, or consensus). The OAEI2019 campaign offered 11 tracks with 29 test cases, and was attended by 20 participants. This paper is an overall presentation of that campaign.

  • 218.
    Algotsson, Daniel
    Linköping University, Department of Computer and Information Science.
    Konstruktion av en databas till stöd för kassaflödesvärdering: Construction of a database to support information management for discounted cash flow valuation of corporations2005Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When a discounted cash flow valuation is performed, the value of the asset is determined by summarising the predicted cash flows and discounting them with the cost of capital. Due to the fact that the future cash flows are predictions, a valuation is always affected by uncertainty. In order to improve the accuracy of the predictions, an extensive amount of information is used. To be successful, it is important to collect reliable and relevant information and manage the information in an efficient way. At present it is difficult to gather and manage information and sufficient computer aid is missing. The purpose of this master thesis is to construct a proposal for a database to support information management for discounted cash flow valuation of corporations. The thesis is conducted with a qualitative research method. An extensive frame of reference is presented in order to give the reader the possibility to get to know both databases and cash flow valuations.

    The result of the study is a conceptual model as well as a logical and physical database model. The proposed database consists of 20 tables where the database relationships connect the value creating factors of the corporation. Possible positive effects of the database are simplified deriving of the corporate value and capacity to store and manage greater amounts of information in a logical manner. The database can also improve the flexibility and adjust the valuation to the dynamic nature of the corporation. Furthermore, the identification of risks and risk factors can be improved. A potential problem with the database is the risk of storing irrelevant information. It can also be difficult to prove a sufficient validity for the database since no user valuation has been carried out.

    In the thesis, the author also argues that the database can be utilised for discounted cash flow valuation of any corporation. However, some tables, attributes and relationships need to be changed and adjusted to the specific nature of the corporation.

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    FULLTEXT01
  • 219.
    Algotsson, Emma
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Design and Evaluation of an E-learning Platform to support Active Learning2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Engineering students at Linköping University are given the opportunity to improve their soft skills through the course Professionalism for Engineers. Soft skills are becoming more and more important in succeeding professionally as well as personally, especially among engineering students, who are more used to improving their hard skills. The course presents the students with a mixture of in-class and out-of-class activities, in which the latter makes use of three different platforms to provide the students with necessary information regarding the course. 

    This study has focused on combining the three platforms by creating a new E-learning platform, where further improvements and additions have been added to create a more supporting environment, in which the out-of-class activities are at the centre. The platform was evaluated through qualitative user tests and the quantitative User Experience Questionnaire, in which four students, enrolled in the course Professionalism for Engineers, participated. Every category in the User Experience Questionnaire received a positive value, implying that the users were overall pleased with the platform and experienced it as being intuitive, efficient and motivating. 

    The proposed platform, with the added functions and design elements, has the potential to support the students in doing their out-of-class activities, and the circumstances whilst doing these activities has been changed to enhance the students' active learning experience. 

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  • 220.
    Algvere, Ebba
    Linköping University, Department of Computer and Information Science.
    Att designa effektivt lärande med blandade lärmiljöer: Hur lärmiljöer och dess aktiviteter inom blandade lärmiljöer påverkar kunskapsutveckling och förtroende för organisationen2019Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [sv]

    Denna studie har undersökt hur olika lärmiljöer inom ett utbildningsupplägg med blandade lärmiljöer skiljer sig i upplevelse, kunskapsutveckling samt förtroende. Vidare har studien undersökt om det finns någon skillnad mellan grupper, med prefererad ordning på lärmiljöer inom ett utbildningsupplägg med blandade lärmiljöer, och prefererad inläringsstil. Fyra olika inläringsstilar, av Honey och Mumford (2000), har använts i studien. Frågeställningarna har undersökts och besvarats genom en triangulering, en kombination av kvalitativa och kvantitativa metoder. Kvalitativ data har samlats in genom semistrukturerade intervjuer och har sedan följt en tematisk analysprocess. Kvantitativ data har erhållits genom ett frågeformulär som sedan har analyserats med statistiska tester. Resultaten från den kvalitativa intervjudelen har visat på att olika lärmiljöer, e-lärande och föreläsning, skiljer sig samt kompletterar varandra med avseende på upplevelse, kunskapsutveckling och förtroende för arbetsgivare. Kvantitativa resultat från frågeformulär har visat på att det inte finns någon signifikant skillnad mellan grupper, som föredrar att börja ett utbildningsupplägg med blandade lärmiljöer med olik första lärmiljö, och styrka i prefererad inläringsstil. Detta innebär att det inte finns någon direkt koppling mellan föredragen ordning på lärmiljöer inom blandade lärmiljöer och prefererad inläringsstil. Denna studie har studerat ett kunskapsgap för hur blandade lärmiljöer bör struktureras. Studiens fynd kan därmed bidra till en bättre förståelse för hur framtida utbildningsupplägg med blandade lärmiljöer bör designas för effektivt lärande och maximal kunskapsutveckling.

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  • 221.
    Alhasan, Ahmed
    Linköping University, Department of Computer and Information Science, The Division of Statistics and Machine Learning.
    Generating Geospatial Trip DataUsing Deep Neural Networks2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Synthetic data provides a good alternative to real data when the latter is not sufficientor limited by privacy requirements. In spatio-temporal applications, generating syntheticdata is generally more complex due to the existence of both spatial and temporal dependencies.Recently, with the advent of deep generative modeling such as GenerativeAdversarial Networks (GAN), synthetic data generation has seen a lot of development andsuccess. This thesis uses a GAN model based on two Recurrent Neural Networks (RNN)as a generator and a discriminator to generate new trip data for transport vehicles, wherethe data is represented as a time series. This model is compared with a standalone RNNnetwork that does not have an adversarial counterpart. The result shows that the RNNmodel (without the adversarial counterpart) performed better than the GAN model dueto the difficulty that involves training and tuning GAN models.

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    Master Thesis
  • 222.
    Alhenawi, Esra'a
    et al.
    Zarqa Univ, Jordan.
    Abu Khurma, Ruba
    Middle East Univ, Jordan.
    Damasevicius, Robertas
    Vytautas Magnus Univ, Lithuania.
    Hussien, Abdelazim
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering. Fayoum Univ, Egypt; Appl Sci Private Univ, Jordan.
    Solving Traveling Salesman Problem Using Parallel River Formation Dynamics Optimization Algorithm on Multi-core Architecture Using Apache Spark2024In: International Journal of Computational Intelligence Systems, ISSN 1875-6891, E-ISSN 1875-6883, Vol. 17, no 1, article id 4Article in journal (Refereed)
    Abstract [en]

    According to Moore's law, computer processing hardware technology performance is doubled every year. To make effective use of this technological development, the algorithmic solutions have to be developed at the same speed. Consequently, it is necessary to design parallel algorithms to be implemented on parallel machines. This helps to exploit the multi-core environment by executing multiple instructions simultaneously on multiple processors. Traveling Salesman (TSP) is a challenging non-deterministic-hard optimization problem that has exponential running time using brute-force methods. TSP is concerned with finding the shortest path starting with a point and returning to that point after visiting the list of points, provided that these points are visited only once. Meta-heuristic optimization algorithms have been used to tackle TSP and find near-optimal solutions in a reasonable time. This paper proposes a parallel River Formation Dynamics Optimization Algorithm (RFD) to solve the TSP problem. The parallelization technique depends on dividing the population into different processors using the Map-Reduce framework in Apache Spark. The experiments are accomplished in three phases. The first phase compares the speedup, running time, and efficiency of RFD on 1 (sequential RFD), 4, 8, and 16 cores. The second phase compares the proposed parallel RFD with three parallel water-based algorithms, namely the Water Flow algorithm, Intelligent Water Drops, and the Water Cycle Algorithm. To achieve fairness, all algorithms are implemented using the same system specifications and the same values for shared parameters. The third phase compares the proposed parallel RFD with the reported results of metaheuristic algorithms that were used to solve TSP in the literature. The results demonstrate that the RFD algorithm has the best performance for the majority of problem instances, achieving the lowest running times across different core counts. Our findings highlight the importance of selecting the most suitable algorithm and core count based on the problem characteristics to achieve optimal performance in parallel optimization.

  • 223.
    Alhola, Sini
    Linköping University, Department of Computer and Information Science.
    Unraveling interaction between tinnitus symptoms, cognitive abilities, and mental disorders2019Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    Based on the former studies, there is evidence of tinnitus being associated with performance on cognitive ability tests (for example Andersson et al. 2009, Hallam et al. 2004). The topic of my bachelor thesis was to unravel how depression, stress and anxiety connected with tinnitus symptoms are related to cognitive abilities such as verbal fluency, inhibition ability and working memory capacity. In order to fill an existing gap of knowledge, the relationship of different severity of stress caused by tinnitus symptoms as measured with Tinnitus Handicap Inventory (THI) and cognitive abilities and depression and anxiety symptoms was emphasized.

    The experiment group was divided into two subgroups, those with lower and higher level of perceived tinnitus severity and the differences in test scores between groups were investigated with one-way analysis of variance. As a result, significant differences between the two tinnitus patient groups were found in the level of performance in inhibition task where participants were asked to give the font color of congruent color - word pair as an answer. It was also studied whether there were correlations between perceived severity of tinnitus symptoms, depression and anxiety symptoms, working memory capacity and inhibition ability. As a result of correlation analysis, this study confirmed the connection between tinnitus symptoms and anxiety and depression symptoms found in previous studies, and a significant correlation was found between THI scores and anxiety symptoms, and THI scores and C inhibition test scores where the participant was asked to name the font color from incongruent color-word pairs. The results of this study suggest that there is a connection between the level of perceived tinnitus severity and the ability to name font color of incongruent color - word pair. The current study found no evidence about the connection between THI scores and other cognitive abilities as well as anxiety and depression symptoms, even though the THI scores correlated with both anxiety symptom scores and with the reaction times of an inhibition task where the participants were asked to point out the font color from incongruent color - word pairs.

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  • 224.
    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

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  • 225.
    Ali, Akhtar
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Comparative study of parallel programming models for multicore computing2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Shared memory multi-core processor technology has seen a drastic developmentwith faster and increasing number of processors per chip. This newarchitecture challenges computer programmers to write code that scales overthese many cores to exploit full computational power of these machines.Shared-memory parallel programming paradigms such as OpenMP and IntelThreading Building Blocks (TBB) are two recognized models that offerhigher level of abstraction, shields programmers from low level detailsof thread management and scales computation over all available resources.At the same time, need for high performance power-ecient computing iscompelling developers to exploit GPGPU computing due to GPU's massivecomputational power and comparatively faster multi-core growth. Thistrend leads to systems with heterogeneous architectures containing multicoreCPUs and one or more programmable accelerators such as programmableGPUs. There exist dierent programming models to program these architecturesand code written for one architecture is often not portable to anotherarchitecture. OpenCL is a relatively new industry standard framework, de-ned by Khronos group, which addresses the portability issue. It oers aportable interface to exploit the computational power of a heterogeneous setof processors such as CPUs, GPUs, DSP processors and other accelerators.

    In this work, we evaluate the eectiveness of OpenCL for programmingmulti-core CPUs in a comparative case study with two CPU specic stableframeworks, OpenMP and Intel TBB, for ve benchmark applicationsnamely matrix multiply, LU decomposition, image convolution, Pi value approximationand image histogram generation. The evaluation includes aperformance comparison of the three frameworks and a study of the relativeeects of applying compiler optimizations on performance numbers.OpenCL performance on two vendor-dependent platforms Intel and AMD,is also evaluated. Then the same OpenCL code is ported to a modern GPUand its code correctness and performance portability is investigated. Finally,usability experience of coding using the three multi-core frameworksis presented.

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  • 226.
    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, p. 65-70Conference 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.

  • 227.
    Ali, Akhtar
    et al.
    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 CPUs2012In: Proceedings of the 5th Workshop on MULTIPROG2012 / [ed] E. Ayguade, B. Gaster, L. Howes, P. Stenström, O. Unsal, HiPEAC Network of Excellence , 2012Conference paper (Refereed)
    Abstract [en]

    Shared memory multicore processor technology is pervasive in mainstream computing. This new architecture challenges programmers to write code that scales over these many cores to exploit the full computational power of these machines. OpenMP and Intel Threading Building Blocks (TBB) are two of the popular frameworks used to program these architectures. Recently, OpenCL has been defined as a standard by Khronos group which focuses on programming a possibly heterogeneous set of processors with many cores such as CPU cores, GPUs, DSP processors. 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. The evaluation includes the effect of compiler optimizations for different frameworks, OpenCL performance on different vendors’ platformsand the performance gap between CPU-specific and GPU-specific OpenCL algorithms for execution on a modern GPU. Furthermore, a brief usability evaluation of the three frameworks is also presented.

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  • 228.
    Ali, Asif
    et al.
    Linköping University, Department of Computer and Information Science.
    Ramzan, Faheem
    Linköping University, Department of Computer and Information Science.
    Analysis and Monitoring of Team Collaboration in Emergency Response Training supported by a Web Based Information Management System2009Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Our objective in this thesis work is to analyze and manage the log files which are generated after a number of experiments series on different groups using C3Fire simulation environment. It includes analyzing and extracting information from log files, and then maintaining this information in a database. This should be presented with a web interface through ICEfaces Ajax framework for Java. Log Files are generated after a number of experiments series on the different groups. All sequences and information related to task performed by team in group is organized in session log files. The work is divided into different steps; first step is to analyze and extract data from log files, and properly arrange it in several different tables in a database, for this MySQL database is used to store the information. The web interface of log file management system is implemented using ICEfaces Ajax framework, and is based on the statistics of log files generated from the C3Fire environment.  User would be able to add/remove the log files, also can view or edit the details of each session log file in database through web interface. Different events can be generated, and logged for the session information.

    C3Fire is an environment that supports training and research in team collaboration. The environment is mainly used in command, control and communication research, and in training of team decision making. Many humanitarian relief operations are doing their work without having any practice. When some disaster events occur, they cannot perform their jobs effectively. Effective and efficient relief operation is the need of humanity; even that’s not enough to move teams to the disaster place at right time; communication and co-ordination among the team members is the big factor to make effective and well-organized work. C3Fire is a simulation system which provides the training for team members to handle such type of disaster events, and makes the work more proficient at that time by doing effective coordination.

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  • 229.
    Ali Kadhum, Bashir
    Linköping University, Department of Computer and Information Science.
    Gamification of reading aloud using Godot and Web speech2022Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Immersion is a subject studied in various areas and especially in games, since a game that immerses a player, counts as a game of great value. Many studies have been performed to understand how to measure immersion through various forms of questionnaires, but how can one with the help of gamification and loud reading make reading more immersive? To see if gamification and loud reading can make reading more immersive an application is developed, the application provides a paragraph, and when read loud correctly creates sound and shows images. Then the application is tested by a group of people to see if gamification can be used to bring life to reading and further immerse the reader in the world of books.  

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    Thesis
  • 230.
    Ali Mousa, Jaffer
    et al.
    Linköping University, Department of Computer and Information Science.
    Salim, Saleh
    Linköping University, Department of Computer and Information Science.
    Developing a web application for collecting conversations in lab rooms2021Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
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  • 231.
    Ali Mousa, Mohammad
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Nguyen, Bertil
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Prestandaeffektivisering av webbapplikation för journalföring2021Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [sv]

    Webbapplikationer är ett smidigt sätt för företag att effektivisera sina tjänster. Det finns flera faktorer som utgör användarens intryck av webbapplikationen. I detta arbete kommer vi att fördjupa oss inom prestanda. I detta arbete kommer en journalföringsapplikation implementeras för att sedan applicera prefetching och cacheing på denna webbapplikation. För att få insikt över huruvida dessa tekniker påverkade applikationen positivt mättes implementationerna med optimeringar separat från grundimplementationen. Resultatet visar på att både cacheing och prefetching hade positiv effekt på prestandan I webbapplikationen. Däremot finner vi att det är viktigt att klargöra vad man vill cachea och prefetcha eftersom i vår implementation av dessa optimeringstekniker får en bättre presterande applikation på bekostnad av användarvänlighet. 

  • 232.
    Alirezaie, Marjan
    Linköping University, Department of Computer and Information Science.
    Semantic Analysis Of Multi Meaning Words Using Machine Learning And Knowledge Representation2011Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    The present thesis addresses machine learning in a domain of naturallanguage phrases that are names of universities. It describes two approaches to this problem and a software implementation that has made it possible to evaluate them and to compare them.

    In general terms, the system's task is to learn to 'understand' the significance of the various components of a university name, such as the city or region where the university is located, the scienti c disciplines that are studied there, or the name of a famous person which may be part of the university name. A concrete test for whether the system has acquired this understanding is when it is able to compose a plausible university name given some components that should occur in the name.

    In order to achieve this capability, our system learns the structure of available names of some universities in a given data set, i.e. it acquires a grammar for the microlanguage of university names. One of the challenges is that the system may encounter ambiguities due to multi meaning words. This problem is addressed using a small ontology that is created during the training phase.

    Both domain knowledge and grammatical knowledge is represented using decision trees, which is an ecient method for concept learning. Besides for inductive inference, their role is to partition the data set into a hierarchical structure which is used for resolving ambiguities.

    The present report also de nes some modi cations in the de nitions of parameters, for example a parameter for entropy, which enable the system to deal with cognitive uncertainties. Our method for automatic syntax acquisition, ADIOS, is an unsupervised learning method. This method is described and discussed here, including a report on the outcome of the tests using our data set.

    The software that has been implemented and used in this project has been implemented in C.

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    FinalThesis
  • 233.
    Alirezaie, Marjan
    et al.
    Institutionen för naturvetenskap och teknik , Örebro Universitet.
    Hammar, Karl
    Högskolan i Jönköping, JTH, Datateknik och informatik.
    Blomqvist, Eva
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Nyström, Mikael
    Linköping University, Department of Biomedical Engineering, Division of Biomedical Engineering. Linköping University, Faculty of Science & Engineering.
    Ivanova, Valentina
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    SmartEnv Ontology in E-care@home2018In: SSN 2018 - Semantic Sensor Networks Workshop: Proceedings of the 9th International Semantic Sensor Networks Workshopco-located with 17th International Semantic Web Conference (ISWC 2018) / [ed] Maxime Lefrançois, Raúl Garcia Castro, Amélie Gyrard, Kerry Taylor, CEUR-WS , 2018, Vol. 2213, p. 72-79Conference paper (Refereed)
    Abstract [en]

    In this position paper we briefly introduce SmartEnv ontology which relies on SEmantic Sensor Network (SSN) ontology and is used to represent different aspects of smart and sensorized environments. We will also talk about E-carehome project aiming at providing an IoT-based health-care system for elderly people at their homes. Furthermore, we refer to the role of SmartEnv in Ecarehome and how it needs to be further extended to achieve semantic interoperability as one of the challenges in development of autonomous health care systems at home.

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    SmartEnv Ontology in E-care@home
  • 234.
    Al-kfairy, Mousa
    Linköping University, Department of Computer and Information Science.
    Toward Agile development methods & Non-functional requirements2009Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    In this thesis, we tried to solve those problems by adapting agile development methods with Non-functional requirements-framework (NFR-Framework).

    In this thesis, we have inspected many research papers, and we have met industrial experts for feedback regarding our theoretical results.

    As a result of the inspection, we have been able to adapt agile development methods (extreme programming (XP)) with NFR-framework. We use XP since it is more practically oriented process than other agile development methods.

    In the first try for this process model, we got three alternatives for applying it. The first one is based on collecting all NFRs from the beginning of the development process. The second one is based on updating the SIG (software interdependency graph) every time we have new functional requirements (FR) and the third one is based on the incremental nature of agile development methods.

    Each one of these alternatives has it is own advantages and disadvantages. We tried to extract those advantages and disadvantages by brainstorming and reading research papers. The most important issue in all of the three alternatives is the applicability. Finally we got industrial feedback regarding all of them.

    As a result of the industrial feedback, we were able to find another alternative of how to apply the process model which is presented in 7.2.

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  • 235.
    Allander, Karin
    Linköping University, Department of Computer and Information Science.
    The influence of working memory on the quality of linguistic predictions during speech understanding in adverse listening conditions: Comparing cortical responses using MEG2022Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    Speech understanding is a fundamental human ability that enable flexible communication among individuals. Understanding natural speech in normal conditions is a fast and automatic process. It is facilitated through integration between prior knowledge about a speech signal and multimodal speech inputs. In situations where listening conditions are adverse, for example due to hearing impairment or environmental noise, speech understanding is challenged and reliance on prior knowledge increases. Prior knowledge about phonology and semantics are involved in predictive mechanisms that generates more successful speech understanding. Working memory processing seems to be involved in influencing the quality of such predictions. To evaluate the role of working memory in the quality of linguistic predictions, a cortical comparison using MEG was used. MEG data from a previous experiment, where participants performed an auditory sentence completion task with background noise was analyzed. Results from statistical analysis, time-domain analysis and time frequency analysis suggests that differences in working memory processing does not influence the quality of linguistic predictions. Further research is required to assess what factors are involved in the quality of linguistic predictions which could lead to unsuccessful speech understanding, in order to improve communication in everyday situations.  

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  • 236.
    Allard, Olof
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Arts and Sciences.
    Katastrofisk design: Ett designförslag för en digital scenarioeditor2014Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [sv]

    Målet med det här arbetet var att skapa en konceptuell designprototyp för en scenarioeditor åt en digital version av utbildningsverktyget Emergo Train System. Rapporten ämnar ta upp och presentera den arbetsprocess som lett fram till designprototypen och dess utvärdering. I rapporten tillkommer även en diskussion kring hur en scenarioeditor bör utformas för att stödja skapandet av ETS-scenarion samt hur ett flexibelt arbetssätt stöds i form av skapandet av scenariorepresentationer.

    Intervjuer genomfördes med instruktörer och systemansvarige för ETS, samt observationer av iordningställande av ett ETS-scenario. Datainsamlingen analyserades och resulterade i en kravspecifikation för den digitala scenarioeditorn. Den prototyp som utformades gjordes så i pappersformat och utvärderades tillsammans med personal från Katastrofmedicinskt centrum i Linköping. 

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  • 237.
    Allmér, Caroline
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Arts and Sciences.
    Utvärdering av en interaktiv brand- och räddningsinstruktion genom tematisk analys baserad på användarintervjuer och heuristisk utvärdering2013Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [sv]

    Syftet med rapporten är att utvärdera en interaktiv brand- och räddningsinstruktion som framförallt används inom försvarsmakten. Utvärderingen gick ut på att ta reda på hur användarna använder instruktionen och hur de vill att den ska utvecklas i framtiden för att möta deras behov. Utvärderingen genomfördes genom intervjuer med sju användare från olika delar av landet samt en heuristisk utvärdering utifrån Nielsens tio användbarhetsprinciper och med hänsyn till Sweller och Chandlers ”cognitive load theory”. Resultatet visade att instruktionen framförallt används som uppslagsbok och att användarna vill se en utveckling av instruktionen där den blir större och omfattar mer information, till exempel om haverier och utländska luftfartyg och att text och illustrationer i instruktionen är uppdaterad och korrekt. Utifrån analysen togs flertalet utvecklingsförslag fram och presenteras i slutet av rapporten.

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    utvardering av en interaktiv brand och raddningsinstruktion
  • 238.
    Alm, Helen
    Linköping University, Department of Computer and Information Science.
    Duk i buk: Functional Resonance Accident Model i en vårdrelaterad kontext2008Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Ett stort antal människor dör på grund av skador som de fått inom vården och som hade kunnat förebyggas. Det finns siffror som pekar på att dessa vårdskador överskrider antalet döda i trafiken. Vid Östergötlands landsting finns sedan år 2005 en fast enhet som arbetar med patientsäkerhet. En av deras uppgifter är att, tillsammans med berörd verksamhet, utföra händelseanalyser inför anmälningar av Lex Maria-fall. Den analysmetod som används av patientsäkerhetsenheten är uppbyggd på en epidemiologisk olycksmodell.

    Syftet med denna studie har varit att använda analysmetoden FRAM (Functional Resonance Accident Model), som är en systemisk analysmetod utarbetad av Erik Hollnagel, i en vårdrelaterad kontext, någonting som inte har gjorts tidigare. FRAM har applicerats på en händelse under en operation då material glömdes kvar i patientens buk. Samtidigt har patientsäkerhetsenheten analyserat samma händelse med sin metod. En jämförelse mellan de två olika analysmetodernas slutsatser har gjorts.

    För insamling av information om arbetet i operationssal har en triangulering av observation, intervjuer med sakkunniga och genomgång av viss dokumentation genomförts. De personer som varit inblandade i den aktuella händelsen har intervjuats av patientsäkerhetsenhetens analysteam. När de båda analyserna var genomförda ordnades en fokusgrupp med diskussion kring analysmetoder.

    Studien har visat att FRAM kan vara lämplig för tillämpning på vårdskador. Det finns fördelar med en systemisk analysmetod som FRAM då den i större utsträckning speglar den omfattande komplexitet som, i detta fall, en operationssal och dess omgivning består av. Detta medför dock att analysprocessen blir mer omfattande och krävande. I dagsläget används landstingets analysmetod av ett stort antal människor efter en relativt kort utbildning, vilket skulle vara svårt att genomföra med FRAM. Det är även tydligt att mer forskning behövs då FRAM är en relativt ny analysmetod under utveckling.

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    FULLTEXT01
  • 239.
    Alm, Jesper
    et al.
    Linköping University, Department of Computer and Information Science.
    Chou Chen, Johan
    Linköping University, Department of Computer and Information Science.
    Danho, Sparel
    Linköping University, Department of Computer and Information Science.
    Ekblom, Axel
    Linköping University, Department of Computer and Information Science.
    Karlén, Jacob
    Linköping University, Department of Computer and Information Science.
    Renström, Emilia
    Linköping University, Department of Computer and Information Science.
    Solvang Stoltz, Oskar
    Linköping University, Department of Computer and Information Science.
    Tegström, Mikaela
    Linköping University, Department of Computer and Information Science.
    En studie om navigerbarhetens påverkan på användbarhet och användares tilltro till e-handel för begagnad kurslitteratur2021Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    The rise of e-commerce in combination with an increased interest in second-hand products have resulted in multiple marketplaces where buyers and sellers can meet. One area where marketplaces of this kind is used is course litterature, where students often buy and sell used books. The purpose of this report is to study how a web application for buying and selling second-hand course litterature can be designed to affect the perceived usability and trust mainly based on navigability. During the development stage, two user tests were conducted to study how the introduction of new functionality and design affected the usability and trust of the web application. The test results indicate that a website’s search functionality can affect its perceived navigability both negatively and positively depending on how well it meets the users’ expectations. Furhermore, the test results confirm the theory about the importance of link- and button-labels for website navigability.

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  • 240.
    Alm, Johan
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Utveckling av 2D matematikpusselspel med Phaser.io2015Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [sv]

    Det finns idag många verktyg och ramverk för att utveckla spelapplikationer. I den här rapporten kommer jag utvärdera Phaser.io som är ett öppen källkodsramverk för att utveckla webspelsapplikationer.

    Resultatet av det här examensarbetet är en prototyp av spelet Equamem som jag har utvecklat utifrån min handledare Erik Berglunds spelkoncept och design. Equamem är en HTML5 webspelsprototyp utvecklat med ramverket Phaser.io med HTML5 och JavaScript.

    I rapporten kommer jag gå igenom olika designval som gjorts och itererats under spelprototypens versioner av utveckling. Jag kommer även utforska hur man utvecklar ett intressant och lättlärt matematikpusselspel.

    Rapporten kommer innehålla information om Phaser.io, vad det är och vad det erbjuder för funktionalitet och hur jag har använt det i utvecklingen av Equamem. Jag kommer gå igenom fördelar och nackdelar med att använda ramverkets funktioner och utvärdera hur väl lämpat det har för att utveckla spel som Equamem.

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  • 241.
    Alm, Therese
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Science & Engineering.
    Design av en användarvänlig Androidapplikation för trådlös kommunikation med Electronic Control Unit för bil eller testmiljö2015Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This thesis has been carried out within the program Bachelor of Computer Science and Engineering at Linköping University in the spring of 2015 performed at the request of ArcCore in Linköping. The aim is to create and design a user friendly Android application which wirelessly can communicate with the electronic control units in a car or test environment.

    The Android application consists of five main screens, four whose task is to print the information travelling on the CAN bus. The five screens are start, fault codes, sensors, ECU Extract and overview. Start will take you to the other screens. Fault codes, print all the fault codes, sensors prints all sensors, the ECU extract prints all information and overview displays a virtual dashboard. User Evaluations have been conducted to develop both the design and layout of the application. The development process is executed by using extreme programming and the evaluations have been carried out with the help of traditional usability tests and binary success. The evaluations feedback has been used to develop both the design and the user friendliness of the application.

    The application has been developed in the Android Studio and communicates with the ECUs using a PEAK PCAN Wireless Gateway which is connected to the Hercules Development Kit TMS570 MCU.

    The result is that we can clearly see that the ease of use has increased during the development process and that we now by using evaluations have a nice and easy user-friendly Android application that can be used by all who wants to get the information available on the CAN bus.

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  • 242.
    Alm, Torbjörn
    et al.
    Linköping University, Department of Management and Engineering, Industrial ergonomics. Linköping University, The Institute of Technology.
    Kovordányi, Rita
    Linköping University, Department of Computer and Information Science, CSELAB - Cognitive Systems Engineering Laboratory. Linköping University, The Institute of Technology.
    Ohlsson, Kjell
    Linköping University, Department of Management and Engineering, Industrial ergonomics. Linköping University, The Institute of Technology.
    Continuous versus Situation-dependent Night Vision Presentation in Automotive Applications2006Conference paper (Refereed)
    Abstract [en]

    As the number of advanced driver assistance systems in modern cars increases the question of possible negative behavioral adaptation is raised. We have investigated this phenomenon for night vision systems in a driving simulator. One common opinion is that there is a risk for using the enhanced visual conditions that come with these systems to increase speed during nighttime driving and thereby eliminate the safety margins the system was designed to provide. In our study two system approaches were compared, one with continuous presentation and one with presentation only when dangerous objects were detected by the system. The latter approach was meant to minimize the risk of negative adaptation, which was partly confirmed in the study. Moreover, the results showed better and more consistent driver performance with the situation-dependent system and all subjects preferred this approach from a workload perspective.

  • 243.
    Alm, Torbjörn
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Industrial Ergonomics.
    Ohlsson, Kjell
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Industrial Ergonomics.
    Kovordanyi, Rita
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, CSELAB - Cognitive Systems Engineering Laboratory.
    Glass Cockpit Simulators - Tools for IT-based Car Systems Design and Evaluation2005Conference paper (Refereed)
  • 244.
    Almgren, Kristian
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Arts and Sciences.
    Dubbeldokumentation i patientjournalen: varför sker det?2013Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [sv]

    Landstinget i Östergötland har problem med ständigt växande informationsmängder i patienters journaler. Anledningen till att detta är ett problem är att journalen blir svår att överblicka vilket gör det svårt för exempelvis läkare och sjuksköterskor att snabbt hitta relevant information och skaffa sig en uppfattning om patientens sjukdomshistoria vid exempelvis patientmottagning. Informationsöverflödet gör patientjournalen ostrukturerad och därmed svår att söka i. Det tar lång tid att hitta specifika data som eftersöks vilket kan leda till frustration och irritation i den redan tidsmässigt pressade arbetsdagen. Enligt tidigare studie är dubbeldokumentation i patientjournalen en stor bidragande faktor till detta problem. Syftet med denna studie är att undersöka varför problemet uppstår, dvs. orsaken till dubbeldokumentation.

    Både observation och intervju har använts som datainsamlingsmetod. Data har sedan analyserats med tematisk analys.

    Studien resulterade i sex olika teman; The Efficiency-Thoroughness Trade-Off Principle (ETTO), Strategier, Uppdatering och Bekräftelse, Dubbeldokumentation, Störningar, Artefakter.

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  • 245.
    Almgren, Magnus
    et al.
    Department of computer science and engineering, Chalmers university of technology, Gothenburg.
    Andersson, Peter
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Björkman, Gunnar
    Stockholms stad / Kungliga Tekniska Högskolan, KTH, Stockholm.
    Ekstedt, Mathias
    Industrial Information and Control Systems, Royal Institute of Technology, KTH, Stockholm.
    Hallberg, Jonas
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Westring, Eric
    FOI, Swedish Defence Research Agency, Linköping, Sweden.
    RICS-el: Building a National Testbed for Research and Training on SCADA Security2019In: Critical Information Infrastructures Security: 13th International Conference, CRITIS 2018, Kaunas, Lithuania, September 24-26, 2018, Revised Selected Papers / [ed] Eric Luiijf, Inga Žutautaitė and Bernhard Hämmerli, Springer, 2019, p. 219-225Chapter in book (Refereed)
    Abstract [en]

    Trends show that cyber attacks targeting critical infrastructures are increasing, but security research for protecting such systems are challenging. There is a gap between the somewhat simplified models researchers at universities can sustain contra the complex systems at infrastructure owners that seldom can be used for direct research. There is also a lack of common datasets for research benchmarking. This paper presents a national experimental testbed for security research within supervisory control and data acquisition systems (SCADA), accessible for both research training and experiments. The virtualized testbed has been designed and implemented with both vendor experts and security researchers to balance the goals of realism with specific research needs. It includes a real SCADA product for energy management, a number of network zones, substation nodes, and a simulated power system. This environment enables creation of scenarios similar to real world utility scenarios, attack generation, development of defence mechanisms, and perhaps just as important: generating open datasets for comparative research evaluation.

  • 246.
    Almgren, Robert
    et al.
    Linköping University, Department of Computer and Information Science.
    Lidekrans, Robin
    Linköping University, Department of Computer and Information Science.
    Transformation of Directed Acyclic Graphs into Kubernetes Deployments with Optimized Latency2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In telecommunications, there is currently a lot of work being done to migrate to the cloud, and a lot of specialized hardware is being exchanged for virtualized solutions. One important part of telecommunication networks that is yet to be moved to the cloud is known as the base-band unit, which sits between the antennas and the core network. The base-band unit has very strict latency requirements, making it unsuitable for out-of-the-box cloud solutions. Ericsson is therefore investigating if cloud solutions can be customized in such a way that base-band unit functionality can be virtualized as well. One such customization is to describe the functionality of a base-band unit using a directed acyclic graph (DAG), and deploy it to a cloud environment using Kubernetes.

    This thesis sets out to take applications represented using a DAG and deploy it using Kubernetes in such a way that the network latency is reduced when compared to the deployment generated by the default Kubernetes scheduler. The problem of placing the applications onto the available hardware resources was formulated as an integer linear programming problem. The problem was then implemented using Pyomo and solved with the open-source solver GLPK to obtain an optimized placement. This placement was then used to generate a configuration file that could be used to deploy the applications using Kubernetes.

    A mock application was developed in order to evaluate the optimized placement. The evaluation carried out in this thesis shows that the optimized placement obtained from the solution could improve the average round-trip latency of applications represented using a DAG by up to 30% when compared to the default Kubernetes scheduler.

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  • 247.
    Almquist, Isak
    et al.
    Linköping University, Department of Computer and Information Science.
    Bark, Mattis
    Linköping University, Department of Computer and Information Science.
    Johansson, Christoffer
    Linköping University, Department of Computer and Information Science.
    Lindell, Philip
    Linköping University, Department of Computer and Information Science.
    Lindholm, Sara
    Linköping University, Department of Computer and Information Science.
    Phung, Stefan
    Linköping University, Department of Computer and Information Science.
    Sundqvist, Johan
    Linköping University, Department of Computer and Information Science.
    Varis, David
    Linköping University, Department of Computer and Information Science.
    Utformning och implementation av tidsrapporterings- och schemaläggningssystem för småföretag2020Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    The construction industry is facing increased digitalization. Companies in the construction industry are currently using analogous and digital solutions for the time reporting and scheduling. The report investigates these solutions by using a web application that examines how solutions ought to be implemented such that the user perceives them as effective and satisfying. To measure usability, the web application was tested on 16 high school students from a construction industry based high school programme. In the user tests the students were handed a set of problems to solve on the web application and were asked to solve them by themselves. The users’ efficiency in navigating the web application was measured with efficiency indicators. After testing, the users evaluated the web application using a SUS-test, carried out with a survey. The study found a low efficiency value in parts of the web application that did not follow the “three-click rule”, including poorly described link titles, and generally had a deep hiearachy structure. The SUS-test scored an 84 out of 100, which means the ERP-system gave a high impression of usability and satisfaction. To develop a time report- and scheduling system that is perceived as usable and satisfying to use, the report concludes that one should use a wide design hierarchy, use clearly described link titles, follow the “three-click rule”, and gather data of the intended user before the design is made.   

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  • 248.
    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.

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    fulltext
  • 249.
    Almquist, Mathias
    et al.
    Linköping University, Department of Computer and Information Science.
    Almquist, Viktor
    Linköping University, Department of Computer and Information Science.
    Analysis of 360° Video Viewing Behaviours2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis we study users' viewing motions when watching 360° videos in order to provide information that can be used to optimize future view-dependent streaming protocols. More specifically, we develop an application that plays a sequence of 360° videos on an Oculus Rift Head Mounted Display and records the orientation and rotation velocity of the headset during playback. The application is used during an extensive user study in order to collect more than 21 hours of viewing data which is then analysed to expose viewing patterns, useful for optimizing 360° streaming protocols. 

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  • 250.
    Almquist, Mathias
    et al.
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Almquist, Viktor
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Krishnamoorthi, Vengatanathan
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Carlsson, Niklas
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Eager, Derek
    Univ Saskatchewan, Canada.
    The Prefetch Aggressiveness Tradeof in 360 degrees Video Streaming2018In: PROCEEDINGS OF THE 9TH ACM MULTIMEDIA SYSTEMS CONFERENCE (MMSYS18), ASSOC COMPUTING MACHINERY , 2018, p. 258-269Conference paper (Refereed)
    Abstract [en]

    With 360 degrees video, only a limited fraction of the full view is displayed at each point in time. This has prompted the design of streaming delivery techniques that allow alternative playback qualities to be delivered for each candidate viewing direction. However, while prefetching based on the users expected viewing direction is best done close to playback deadlines, large buffers are needed to protect against shortfalls in future available bandwidth. This results in conflicting goals and an important prefetch aggressiveness tradeoff problem regarding how far ahead in time from the current playpoint prefetching should be done. This paper presents the first characterization of this tradeoff. The main contributions include an empirical characterization of head movement behavior based on data from viewing sessions of four different categories of 360 degrees video, an optimization-based comparison of the prefetch aggressiveness tradeoffs seen for these video categories, and a data-driven discussion of further optimizations, which include a novel system design that allows both tradeoff objectives to be targeted simultaneously. By qualitatively and quantitatively analyzing the above tradeoffs, we provide insights into how to best design tomorrows delivery systems for 360 degrees videos, allowing content providers to reduce bandwidth costs and improve users playback experiences.

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