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  • Presentation: 2018-03-23 10:00 Hörsal L1, Stockholm
    Milosevic, Jezdimir
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Model Based Impact Analysis and Security Measure Allocation for Control Systems2018Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Improvement of cyber-security of industrial control systems is of utmost importance for our society. It has been recognized that many security vulnerabilities can be found in these systems, which if exploited may lead to dire consequences. For instance, successful cyber-attacks against industrial control systems may cause loss of electricity, lead to shortage of drinkable water,or disrupt oil and gas production. Deploying security measures to protect industrial control systems may be costly.  Thus, it is expected that we would not be able to prevent all the security vulnerabilities that we find within the systems. In this thesis, we consider two problems related to this issue. The first one is how to determine which combinations of vulnerabilities are the most critical to be prevented. An important part of this classification is estimating the impact of cyber-attacks conducted using these vulnerabilities, which is the first major problem considered in the thesis. The budget for deploying security measures can then be focused on preventing the most critical combinations of vulnerabilities that are found. How to do this in an optimal way once the number of vulnerabilities and measures is large is the second major problem considered. As our first contribution, we outline a framework for estimating the attack impact in industrial control systems. Here, we consider industrial control systems that have both control and monitoring tasks. For industrial control systems with control tasks, we propose a framework to estimate the impact of several attack strategies. We prove that the estimation of the impact of all possible strategies is reducible to solving a set of convex minimization problems. The solvers for convex minimization problems are well known, so the exact value of the attack impact can be obtained easily. For industrial control systems with monitoring tasks, we analyze the impact of a bias injection attack strategy.  We prove that the attack impact can be obtained as the solution of a quadratically constrained quadratic program, for which the exact solution can be found efficiently. We also introduce a lower bound of the attack impact in terms of the number of compromised sensors. The theoretical findings are illustrated in numerical examples. As our second contribution, we propose a flexible modeling framework for allocating security measures. Our framework is suitable for dynamical models of industrial control systems, and can be used in cases when the number of vulnerabilities and measures is large. The advantages of our framework are the following. Firstly, the framework includes an algorithm for efficiently finding the most dangerous vulnerabilities in the system. Secondly, the problem of eliminating these vulnerabilities can provably be casted as a minimization of a linear function subject to a submodular constraint. This implies that the suboptimal solution of the problem, with guaranteed performance, can be found using a fast greedy algorithm. The applicability of the framework is demonstrated through simulations on an industrial control system used for regulating temperature within a building

  • Presentation: 2018-03-26 10:00 L52, Stockholm
    Ringenson, Tina
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Strategic Sustainability Studies.
    How municipalities can work with digitalisation for environmental aims2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Humanity is facing big environmental challenges. Apart from the climate changes, there is also an ongoing depletion of the natural resources necessary for our survival in general, and for highly electronics-dependant lifestyles especially. At the same time, both urbanisation and digitalisation are progressing at a rapid pace. Digitalisation holds a potential to decrease environmental impact from cities and urban lifestyles, and many cities want to increase their use of digital technologies and services. This is often at least partially motivated by environmental concerns. In these cases, it is often the municipality that is responsible for strategies and support of increased digitalisation.

    This dissertation places itself in the Smart Sustainable City field, but more specifically aims to support municipalities’ work with digitalisation for environmental goals. The results are structured around three parts. The first part accounts for six cities’ promising digital solutions with possible environmental benefits, and of possible digital tools to support two EU directives that can affect municipalities’ environmental work. The second part suggests how municipalities can work with digitalisation for environmental goals, and especially stresses evaluation and strategic investments. The third part looks at possible long-term societal changes in relation to digitalisation, and the risks with a city depending on electronics: It is important that a city can remain adequately functional, even in the case of a short- or long term shortage of resources and/or energy.

    Finally, I discuss some of the uncertainties in digitalisation for environmental goals. There are uncertainties regarding digitalisation’s actual effects, which can make it harder to know what investments to make. Implementing digital technologies for municipal aims often demands cooperation between actors with different interests, but if the municipality relates its decision to environmental goals, it facilitates demanding that digital services and tools have environmental benefits.

  • Presentation: 2018-04-09 10:00 Auditorium-Q2, Stockholm
    de Alwis, Pahansen
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Naval Systems.
    On Evaluation of Working Conditions aboard High-Performance Marine Craft2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    High-Performance Marine Craft (HPMC) is a complex system confronted by the stochastic nature of the waves challenging the safety of life at sea. The personnel aboard these craft are vulnerable to detrimental conditions, in fact, limiting the system’s performance evoking the significance of the Human Factors Integration (HFI) in the design and operation of these craft. The risks related to the work environments at sea have inadequately been investigated. A consistently identified fact is that the exposure to work environments containing vibration and repeated shock elevates the risk of adverse effects on human health and performance. In the event that the exposure risk is known, the situation can be managed by the operators and the legislated health and safety demands can be achieved by the employer. Moreover, when quantification of the exposure-effect relationships is potential, human factors, in terms of health and performance, can be integrated into HPMC design and operation. However, the knowledge is limited about the adverse health and performance effects among the High-Performance Marine Craft Personnel (HPMCP), the factors causing theses effects and their relationships.

    The thesis presents a holistic approach for the integration of human factors, in terms of health and performance, into HPMC design and operation. A research program has been designed branching the design and operational requirements of HPMC concerning HFI. A method is introduced for a real-time crew feedback system, which monitors and characterizes vibration and shock conditions aboard HPMC, enabling determination of the risk of acute injuries due to the high-intensity instantaneous impact exposure and the acquired risk of adverse health and performance effects due to the accumulated vibration exposure. This brings forth the requirement of epidemiological studies in order to strengthen the exposure-effect relationships. Therefore, web-based questionnaire tools are developed, validated and pilot tested for cross-sectional and longitudinal investigation of health and performance in HPMCP. The work exposure is measured aboard HPMC in terms of vibration and investigated in relation to the adverse health and performance event onsets, and the ride perception of the personnel aboard.

    The introduced method for the real-time crew feedback is capable of informing the exposure risk in terms of human health and performance. The questionnaire tools are feasible for epidemiologically surveying HPMCP and similar populations providing data for investigating adverse health and performance effects, risk factors and their relationships. Promising trends are observed between the quantified work exposure and the health and performance onsets, and the human perception.

    The work will be continued to identify the exposure-effect relationships facilitating better use of the existing standards, supporting ongoing development of the existing standards and providing information to draw appropriate design and operational limits in rules and regulations.

  • Presentation: 2018-04-13 09:30 M108, Stockholm
    Zangeneh Kamali, Abbas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges. ELU Konsult AB.
    Dynamic Soil-Structure Interaction Analysis of Railway Bridges: Numerical and Experimental Results2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work reported in this thesis presents a general overview of the dynamic response of short-span railway bridges considering soil-structure interaction. The study aims to identify the effect of the surrounding and underlying soil on the global stiffness and damping of the structural system. This may lead to better assumptions and more efficient numerical models for design.A simple discrete model for calculating the dynamic characteristics of the fundamental bending mode of single span beam bridges on viscoelastic supports was proposed. This model was used to study the effect of the dynamic stiffness of the foundation on the modal parameters (e.g. natural frequency and damping ratio) of railway beam bridges. It was shown that the variation in the underlying soil profiles leads to a different dynamic response of the system. This effect depends on the ratio between the flexural stiffness of the bridge and the dynamic stiffness of the foundation-soil system but also on the ratio between the resonant frequency of the soil layer and the fundamental frequency of the bridge.

    The effect of the surrounding soil conditions on the vertical dynamic response of portal frame bridges was also investigated both numerically and experimentally. To this end, different numerical models (i.e. full FE models and coupled FE-BE models) have been developed. Controlled vibration tests have been performed on two full-scale portal frame bridges to determine the modal properties of the bridge-soil system and calibrate the numerical models. Both experimental and numerical results identified the substantial contribution of the surrounding soil on the global damping of short-span portal frame bridges. A simplified model for the surrounding soil was also proposed in order to define a less complicated model appropriate for practical design purposes.