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  • Public defence: 2020-02-21 13:15 9C 203, Karlstad
    Wendell, Joakim
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Centre for the Studies of Social Sciences Didactics (from 2013). Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Political, Historical, Religious and Cultural Studies (from 2013).
    Teaching and Learning Historical Explanation: Teacher and Student Cases from Lower and Upper Secondary History2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The purpose of this thesis is to investigate and analyse how teachers and students understand the concept of historical explanation in the context of classroom teaching practices. The thesis is made up of four studies that investigate different aspects of understanding, focusing on either teacher or student understanding as expressed in words and actions.

     

    The different studies employ differing methods, including classroom observations, interviews with teachers, and analysis of student answers to prompts intended for assessment. The studies include cases from both lower and upper secondary school in Sweden. The four studies provide empirical results that are presented in each individual study, and furthermore subjected to an aggregated analysis in order to find patterns of commonality. The aggregated analysis draws upon Rüsen's theory of historical knowledge, as well as a progression model for historical explanation based on results from previous research.

     

    The results of the study show a clear difference between lower and upper secondary school in how students at each stage construct historical explanations, indicating differing expectations of what students are supposed to do with explanations in each stage. Teachers' practices are more varied: while a majority of the included teachers manifest a disciplinary understanding of historical explanation, in line with previous research about historical explanation in educational contexts, other approaches with other emphases are also present. These include an emphasis of learning explanations as sets of facts, as well as approaches that aim for making the knowledge of historical explanation useful outside of the history subject. Examples of such aims found in the study are to enhance empathetic understanding of other people, and helping students to orient themselves in relation to present-day issues.

  • Public defence: 2020-02-28 10:15 21A342, Eva Erikssonsalen, Karlstad
    Afzal, Zeeshan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Life of a Security Middlebox: Challenges with Emerging Protocols and Technologies2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Internet of today has intermediary devices known as middleboxes that perform more functions than the normal packet forwarding function of a router. Security middleboxes are a subset of these middleboxes and face an increasingly difficult task to perform their functions correctly. These middleboxes make many assumptions about the traffic that may not hold true any longer with the advent of new protocols such as MPTCP and technologies like end-to-end encryption.

    The work in this thesis focuses on security middleboxes and the challenges they face. We develop methods and solutions to help these security middleboxes continue to function correctly. In particular, we investigate the case of using MPTCP over traditional security infrastructure as well as the case of end-to-end encryption. We study how practical it is to evade a security middlebox by fragmenting and sending traffic across multiple paths using MPTCP. We then go on to propose possible solutions to detect such attacks and implement them. The potential MPTCP scenario where security middleboxes only have access to part of the traffic is also investigated and addressed. Moreover, the thesis contributes a machine learning based approach to help security middleboxes detect malware in encrypted traffic without decryption.

  • Public defence: 2020-03-06 09:15 21A342, Karlstad
    Santos, Ricardo
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Towards Resilient and Reconfigurable Software-defined Wireless Backhaul Networks2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The increase of mobile devices and services over the last decade has led to unprecedented mobile traffic growth. To cope with the increasing demands, fifth generation (5G) network architectures have been designed to provide the required capacity using a large number of small cells (SCs). However, a dense deployment of SCs requires a robust and scalable backhaul to transport the access traffic towards the Internet. In this thesis, we explore the application of the Software-defined Networking (SDN) paradigm for the management of a wireless backhaul. With SDN, the data and control planes are separated and the network is managed by a centralized entity. To that end, we provide multiple contributions that focus on achieving resilient and reconfigurable wireless backhaul networks. Firstly, we propose an SDN-based architecture to manage the wireless backhaul. Our architecture is integrated in practical testbed environments, where we use an SDN controller to configure the forwarding plane and wireless backhaul links. Secondly, we evaluate SDN-based resiliency in the wireless backhaul. We achieve that by implementing fast-failover resiliency with OpenFlow group tables and by using the bidirectional-forwarding detection protocol (BFD) to monitor the state of the backhaul links. Finally, we develop algorithms that calculate the necessary reconfiguration operations to transition between different wireless backhaul topologies, while minimizing the impact on existing user traffic. We consider that the backhaul nodes can be powered on/off and are equipped with steerable antennas that can be aligned to form links with different neighbors. Our optimization problems are modeled as mixed integer linear programs (MILP) that are optimally solved using exact mathematical programming methods. In addition, we develop greedy-based heuristic algorithms that solve the same problems and obtain good quality solutions in short time.