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  • Public defence: 2018-03-20 09:30 Sal Pi, Västerås
    Åkerberg, Anna
    Mälardalen University, School of Health, Care and Social Welfare. Mälardalen University, School of Innovation, Design and Engineering.
    An interactive health technology solution for encouraging physical activity: a first model based on a user perspective2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Globally, the level of physical inactivity is increasing. The overall aim of this thesis was to develop and test a first model of an interactive health technology solution (called App&Move) that should encourage physically inactive adults to be more physically active. App&Move was iteratively developed based on the user perspective, a so-called user-centered design. First, available technology was assessed; the validity and reliability of one smartphone pedometer application and one commonly used traditional pedometer were investigated. It was found that none of the investigated pedometers could measure correctly in all investigated situations. However, measurements by a smartphone appli-cation was identified to have high potential when aimed at monitoring physical activity in everyday situations. As the next step, a questionnaire was developed and distributed in central Sweden. The 107 respondents who answered the questionnaire were divided and analyzed in groups of users and non-users of physical activity self-monitoring technology. The results showed that users and non-users of such technology mainly had similar opinions about desirable functions of the technology. To gain further knowledge concerning how to design App&Move, the target group physically inactive non-users participated in focus group interviews. Important results were that the technology should focus on encouragement rather than measurements and that it preferably should be integrated into already existing technology, if possible already owned and worn by the person. A brainstorming workshop confirmed that the smartphone was a suitable platform, and a decision to develop a smartphone application was taken. A first draft of App&Move was developed, focusing on encouragement and measuring everyday activity and exercise in minutes per day. App&Move was based on available physical activity recommendations and strategies for successful behavior change. App&Move was positively received in a user workshop and thereafter iteratively refined and developed based on further user input. App&Move was usability tested in 23 physically inactive adults who used App&Move for four weeks and answered two questionnaires. Three usability aspects, effectiveness, efficiency and satisfaction, were assessed as follows: acceptable, high and medium, and slight increases in activity minutes were observed during the test period. To conclude, this thesis has investigated the user perspective of physical activity self-monitoring technology with a target group of physically inactive adults. Based on these findings, a behavior change application for smartphone, App&Move, was presented. The usability test indicated promising results with respect to usability and indicated an ability to encourage the users to physical activity to some extent.

  • Public defence: 2018-04-06 10:00 Filharmonin, Eskilstuna
    Raza, Mohsin
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Developing Process Design Methodology for Investment Cast Thin-Walled Structures2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Components for engineering systems, such as gas turbines and jet engines operating at high temperature are usually produced in superalloys. The investment casting process is most widely used for manufacturing these components due to the ability of the process to produce parts with complex geometries to close dimensional tolerances. Other processing routes are less advantageous due to high mechanical strength and hardness of these alloys, which make formability and machining difficult even at high temperature. The global requirements for lower fuel consumption and emissions are increasing the demands to lower the weight of cast components in jet engines. The ability to produce components with lower wall thickness will not only help to reduce the cost of production and resource usage but also help to improve the efficiency of engineering systems resulting in lower fuel consumption and reduced emissions of environmentally hazardous gases. However, casting of thin walled components is challenging due to premature solidification in thin sections and long feeding distances often resulting in incomplete filling, cold shuts and shrinkage porosity.

    The castability of thin-sections is dependent upon selection of appropriate values of casting parameters to achieve favorable conditions for the mould filling and solidification. In foundry environment, fluctuation in these targeted values of casting parameters is common due to semi-automated nature of process. The effects of casting parameters on mould filling and defect formation have been widely reported in the literature, however effect of fluctuations in targeted values of casting parameters resulting from typical variation in the foundry is not well documented. Moreover, the origin of process variation and how to manage them in foundries, especially in relation to thin-walled casting has not been well documented. 

    In this work, the common variations in critical process parameters, originating from foundry practices and equipment are identified. The effect of variations and resulting fluctuation in targeted values of casting parameters on castability of thin-walled castings is evaluated. The casting process is simulated by defining boundary conditions which replicate the foundry conditions and properties of foundry materials in a commercial casting simulation software. The effect of fluctuation of casting parameters on castability of thin-walled castings is established by casting trials as well as simulations and the validity of simulation is evaluated. A methodology to design a casting process is established by proposing methods to minimize the process variation as well as using Design of Experiments (DoE) based simulation work to achieve reliability and repeatability in the process.

    It is concluded that the mould temperature, casting temperature and pouring rate are common casting parameters affected by the variation originating from equipment and the casting practices. The variation in these parameters strongly effects the castability of thin-walled sections. The significance of these variations is validated by simulation and it is concluded that the validity of simulation is not only strongly dependent upon the foundry specific material data but also depends upon setting up valid boundary conditions according to the equipment and practices used. It is also concluded that by introducing material data and accurate boundary conditions, simulation can be used as tool to facilitate process development in foundries. A systematic implementation of simulations based on DoE and optimization resulted in significant reduction in process development time.

    The result of this work has been further developed into a process design methodology for investment casting foundries working with casting of thin-walled castings for high temperature applications. The term process design in this work is defined as design and evaluation of gating system as well as identifying optimized values of casting parameters to cast components in foundry.


  • Public defence: 2018-04-16 13:15 Gamma, Västerås
    Lisova, Elena
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Monitoring for Securing Clock Synchronization2018Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In today's society, more and more embedded computer systems are connecting. There are many different types of embedded systems including industrial networks, Internet of Things (IoT), distributed control systems, connected vehicles, etc. Most such cyber-physical systems (CPS), regardless of their specifics, have a communication part that enables data exchange between system entities and external entities. Today, many commercial systems adopt heterogeneous solutions including a combination of wired and wireless communication. Using both technologies together brings benefits in terms of flexibility and reliability, but it also imposes new challenges, such as maintaining system security. Security of connected CPS therefore becomes paramount to address.

    One of the most critical properties of CPS is related to timing, as the vast majority of all CPS have real-time requirements due to interaction with a physical process, and communication therefore follows some kind of schedule with deadlines. In time-triggered networks, transmissions occur at pre-defined instants in time, but also in event-driven communication, data usefulness can be based on a timestamp, and consequently, to judge data validity and order of events, nodes need to interpret the received timestamp based on its own time. Both implementations make clock synchronization an essential network asset. Therefore, the first step in securing CPS is an investigation of ways to break clock synchronization. The next step is development of a solution that allows detection of malicious influence in the system and mitigates its consequences.

    In this thesis, a threat model and a vulnerability analysis of clock synchronization is built upon IEEE 1588, a standard widely used in industry for establishing and maintaining clock synchronization. As a mitigation strategy, a distributed monitoring solution is proposed to detect if an adversary is influencing clock synchronization in the network. The monitor strategy is based on dynamic rules for switching between different network states: no adversary present, quarantine mode and attack detected. Next, game theory is used to investigate the interaction between an adversary and the monitor. Furthermore, the time chase between an adversary and the monitor is examined to see how the monitor strategy influences the outcome of the adversary actions. Safety and security interaction is also considered to see which implications the proposed security solution has on the safety domain. Finally, the monitoring approach is abstracted and analyzed for different estimations of channel reliability to investigate the applicability of the solution in different settings, and as a result a methodology for black channel state manager design is presented.