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  • Presentation: 2019-01-22 10:00 U61, Stockholm
    Bekele, Abiy
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Application of Automated Non-contact Resonance Testing for Low Temperature Behavior of Asphalt Concrete2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Impact resonance testing is a well-documented non-destructive testing method and its applications on asphalt concrete have also been implemented successfully. The test is carried out manually by inducing an impact in order to excite the test specimen and taking measurements of the vibrational response. In an effort to improve the manual procedure of impact resonance testing, an automated non-contact methodology is developed and its applicability with regards to low temperature behaviors of asphalt concrete is investigated. Results from this work show that repeatable fundamental resonance frequency measurements can be performed on a disc shaped specimen in an automated manner without the need to open the thermal chamber. The measurements obtained from the new method have been verified by taking similar resonance frequency measurements using an instrumented impact hammer. It has also been shown in this work that the proposed method is suitable to investigate the lone effects of cyclic thermal conditioning on asphalt concrete without any other possible biasing effects associated with contact in the conventional testing. A hysteretic behavior of stiffness modulus is obtained on three different asphalt concrete specimens subjected to repeated low temperature cyclic conditioning. Reduced modulus values at each temperature are obtained in all the tested specimens after a low temperature stepwise conditioning at temperatures from 0oC to -40 oC. This observed behavior shows that the dynamic modulus of the tested specimens is affected by low temperature conditioning. The norm of the complex modulus decreases and the phase angle or damping ratio increases after low temperature conditioning. Hence, valuable and practical low temperature characteristics of different asphalt concrete mixtures can possibly be obtained by using the proposed methodology.

  • Presentation: 2019-02-01 14:00 rum A124 , KTH Arkitekturskolan,, Stockholm
    Hällgren, Nina
    KTH, School of Architecture and the Built Environment (ABE), Architecture.
    Designing with Urban Sound: Exploring methods for qualitative sound analysis of the built environment2019Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The licentiate thesis Designing with Urban Sound explores the constitution and qualitative characteristics of urban sonic space from a design-oriented and practice-based perspective. The act of lifting forth and illuminating the interaction between architecture, the creation of sound and a sonic experience aims to examine and develop useful tools and methods for the representation, communication and analysis of the exterior sonic environment in complex architectural spaces. The objective is to generate theoretical and practical knowledge within the field of urban sound planning and design by showing examples of different and complementary ways of communicating and analyzing sound than those which are commonly recognized. 

  • Presentation: 2019-02-07 13:00 Ocean and Pacific, Stockholm
    Johansson, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Strategic Sustainability Studies.
    Towards a sustainable mobility paradigm? An assessment of three policy measures2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Transportation and mobility are important components in the organisation and structure of people´s daily activities, but the transport sector has considerable environmental impacts, e.g. greenhouse gas emissions and land use. Governance of the sector is difficult, as there is an ongoing a shift in governance structures away from hierarchical towards more collaborative governance. Given these challenges, it may be necessary to shift the focus from mobility to accessibility and to adopt a new paradigm in transport planning.

    This thesis critically investigates what a paradigm shift might mean for the Swedish national and municipal transport, housing and parking planning context and examines what a Social Practice Theory framework could contribute in analysing such a paradigm shift. This is done by investigating three different policies that are arguably in line with a shift in planning paradigms.

    All three policy measures open up decision making to different stakeholders or even citizens, reflecting a shift in governance, and all highlight the need to shift the focus from physical infrastructure to accessibility, through collaboration with a range of stakeholders. However, in each case, current conditions and practices render a transition more difficult.

    The Swedish Transport Administration (STA) states the importance of reducing the need to travel and of using existing infrastructure more efficiently, and stipulates that these types of measures should be considered before new infrastructure investments. However, the STA has a limited mandate to finance these measures, resulting in ambiguous signals and frustration among regional STA officials. This thesis shows that making the STA’s mandate more function-oriented would facilitate a transition in line with the sustainable mobility paradigm.

    Another policy measure discussed in the thesis is a shift from minimum parking requirements, where developers are required to build a minimum number of parking spaces, to flexible parking requirements, where the number of parking spaces provided depends on the local context and where other mobility services may replace the need for physical parking spaces. In this thesis, people who have bought apartments in developments with flexible parking requirements were surveyed in order to understand their practices and how they perceive and plan to use the mobility services provided.

    The feasibility of using a new parking management tool, Parking Benefit Districts, in a European context (Stockholm, Sweden) was assessed. In a Parking Benefit Districts system, parking charges are implemented, increased or extended to curb parking, with the revenues being returned to the area where the charges are imposed and with citizens, or other stakeholders, participating in decisions on how to use the revenues. The underlying intention is to increase acceptance of parking charges, as on-street parking charges may be deemed necessary by planners, but are unpopular among citizens and other stakeholders. This thesis shows that there are no legal barriers to implementing a Parking Benefit District programme in Sweden, but there are some limitations on how revenues can be used. Moreover, Sweden does not have this planning tradition and the programme may not be perceived as legitimate. Another important issue is equity and participation, e.g. it is important to consider who to include and how to include them.

    Overall, the policy measures studied involve a shift away from an infrastructure-centred to a people-centred approach. However, other planning practices and institutions may push in different directions. This thesis shows that a Social Practice Theory framework can be useful as a lens through which researchers and policymakers view possible changes needed to achieve a sustainable mobility paradigm.

  • Presentation: 2019-02-14 15:00 FB52, Stockholm
    Alp, Dennis
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Core-collapse Supernovae: Theory vs. Observations2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    A core-collapse supernova (CCSN) is an astronomical explosion that indicates the death of a massive star. The iron core of the star collapses into either a neutron star or a black hole while the rest of the material is expelled at high velocities. Supernovae (SNe) are important for the chemical evolution of the Universe because a large fraction of the heavier elements such as oxygen, silicon, and iron are liberated by CCSN explosions. Another important role of SNe is that the ejected material seed the next generation of stars and planets. From observations, it is clear that a large fraction of all massive stars undergoes SN explosions, but describing how SNe explode has remained a challenge for many decades.

    The attached papers focus on comparing theoretical predictions with observations, primarily observations of SN 1987A. The compact remnant in SN 1987A has not yet been detected and we have investigated how a compact object can remain hidden in the ejecta (Paper I and II). Because of the high opacity of the metal-rich ejecta, the direct X-ray observations are not very constraining even for potentially favorable viewing angles. However, the combined observations still strongly constrain fallback accretion and put a limit on possible pulsar wind activity. The thermal surface emission from a neutron star is consistent with the observations if our line of sight is dust-obscured, and only marginally consistent otherwise. Future observations provide promising opportunities for detecting the compact object.

    We have also compared the most recent three-dimensional neutrino-driven SN models that are based on explosion simulations with early X-ray and gamma-ray observations of SN 1987A (Paper III). The models that are designed to match SN 1987A fit the data well, but not all tensions can be explained by choosing a suitable viewing angle. More generally, the asymmetries do not affect the early emission qualitatively and different progenitors of the same class result in similar early emission. We also find that the progenitor metallicity is important for the low-energy X-ray cuto↵. Current instruments should be able to detect this emission from SNe at distances of 3–10 Mpc, which correspond to distances slightly beyond the Local Group.

  • Presentation: 2019-02-15 14:00 Q2, Stockholm
    Baumann, Dominik
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control. Max Planck Institute for Intelligent Systems.
    Fast and Resource-Efficient Control of Wireless Cyber-Physical Systems2019Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Cyber-physical systems (CPSs) tightly integrate physical processes with computing and communication to autonomously interact with the surrounding environment.This enables emerging applications such as autonomous driving, coordinated flightof swarms of drones, or smart factories. However, current technology does notprovide the reliability and flexibility to realize those applications. Challenges arisefrom wireless communication between the agents and from the complexity of thesystem dynamics. In this thesis, we take on these challenges and present three maincontributions.We first consider imperfections inherent in wireless networks, such as communication delays and message losses, through a tight co-design. We tame the imperfectionsto the extent possible and address the remaining uncertainties with a suitable controldesign. That way, we can guarantee stability of the overall system and demonstratefeedback control over a wireless multi-hop network at update rates of 20-50 ms.If multiple agents use the same wireless network in a wireless CPS, limitedbandwidth is a particular challenge. In our second contribution, we present aframework that allows agents to predict their future communication needs. Thisallows the network to schedule resources to agents that are in need of communication.In this way, the limited resource communication can be used in an efficient manner.As a third contribution, to increase the flexibility of designs, we introduce machinelearning techniques. We present two different approaches. In the first approach,we enable systems to automatically learn their system dynamics in case the truedynamics diverge from the available model. Thus, we get rid of the assumption ofhaving an accurate system model available for all agents. In the second approach, wepropose a framework to directly learn actuation strategies that respect bandwidthconstraints. Such approaches are completely independent of a system model andstraightforwardly extend to nonlinear settings. Therefore, they are also suitable forapplications with complex system dynamics.