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- Cramer, Henriette, et al.
(author)
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Performing a Check-in : Emerging Practices, Norms and ‘Conflicts’ in Location-Sharing Using Foursquare.
- 2011
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In: Proceedings of the 13th Conference on Human-Computer Interaction with Mobile Devices and Services. - Stockholm, Sweden : ACM. - 9781450305419
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Conference paper (other academic/artistic)abstract
- Location-sharing services have a long history in research, but have only recently become available for consumers. Most popular commercial location-sharing services differ from previous research efforts in important ways: they use manual ‘check-ins’ to pair user location with semantically named venues rather than tracking; venues are visible to all users; location is shared with a potentially very large audience; and they employ incentives. By analysis of 20 in- depth interviews with foursquare users and 47 survey responses, we gained insight into emerging social practices surrounding location-sharing. We see a shift from privacy issues and data deluge, to more performative considerations in sharing one’s location. We discuss performance aspects enabled by check-ins to public venues, and show emergent, but sometimes conflicting norms (not) to check-in.
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- Rudmark, Daniel
(author)
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Designing Platform Emulation
- 2021
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Doctoral thesis (other academic/artistic)abstract
- Many contemporary firms and public agencies seek to engage external third-party developers to supply complementary applications. However, this type of development sometimes occurs without organizational consent, which creates problems for subjected organizations at both the technical and organizational levels. In this thesis, I have developed a theoretical perspective called open platform emulation. This perspective builds on emulation logics, where designers use an external model as a basis for developing compatible platform capabilities superior to the original model. In this thesis, this model has been external unsanctioned development. In open platform emulation, such capabilities include governance decisions enabling coherence with previously proven solutions, the flexibility to accommodate new development trajectories, and strategies for applying openness to a digital resource. The means to achieve these capabilities involves design rules’ architecture, interfaces, and integration protocols, which convey the capabilities to third-party developers. This way, a platform owner can draw on governance and architectural configurations to emulate self-resourcing behavior through the platform core. I generated the contributions from this thesis by materializing open platform emulation in a clinical setting. More specifically, I used action design research (ADR) together with the Swedish Transport Administration (STA). Starting in early 2012, I led a platform initiative that, in collaboration with the STA, sought to emulate self-resourcing to design an open platform. Here, I conducted two full ADR cycles that resulted in a currently active production platform used by both the STA and external third-party developers. Before this engagement, I also conducted studies of related phenomena within the Swedish public transport industry, and I have continued to follow the STA’s platform trajectory since its release in 2014. The theoretical contributions from this thesis include design principles that seek to guide the designers of open platforms in situations where digital resources are subject to self-resourcing. These design principles cover both product and process aspects throughout the open platform’s developmental trajectory. Also, I offer additional theoretical implications based on this work. These include extensions to current theories on open platforms, different types of platform emulation, an enunciated influence response to outlaw innovation, and methodological implications for guided emergence in ADR.
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- Finnsgård, Christian, 1974, et al.
(author)
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Costs, not SECAs make RoRo steam slow
- 2017
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In: HANSA International Maritime Journal. - : HANSA. - 0017-7504. ; 154:1, s. 42-43
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Journal article (other academic/artistic)abstract
- The issue of speed is more complex for RoRo/RoPax vessels than other segments. A Swedish research team has addressed the preconditions for introducing slow steaming in Northern Europe and asked operators in Scandinavian waters how they prepared and have acted under SECA
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- Kjell, Gunnar, 1954
(author)
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Estimating Probability Distribution by doing Computer Experiments
- 2000
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Doctoral thesis (other academic/artistic)abstract
- In almost every field of engineering, advanced computer programs are used. In many cases only the probability distributions of the input variables to the programs are known. Sometimes stochastic processes are used as input, for example if the stresses in a construction due to an earthquake are to be calculated. In such cases it is only possible to estimate the distributions of the calculated entities. This can be done by computer simulation, i.e. doing many calculations with different configurations of input variables. As the computing time for each computer run can be long it is important to get an accurate estimate of the distribution of the output variable with a small number of runs. The organization of such computer simulations is called Computer planning. This thesis consists of three papers. The first paper describes how synthetic earthquake time-histories which in mean fulfil given target spectra can be generated. The second paper proposes a new sampling plan, the level-based stratified sampling plan, which can be used if the probability distribution of a system described by a computer code should be estimated by computer simulations. It is shown that estimates from this sampling plan have the lowest variance among estimates from unbiased sampling plans. The third paper discusses the problem of estimating the variance of estimates from the Latin hypercube sampling plan. This sampling plan is widely used and it is well known that its estimates in general have low variance. In the paper similarities between field survey sampling and computer simulations are outlined and methods used for estimating the variance in field survey sampling are examined to se if they also can be used in computer simulations. The difficulties to estimate the variance from a single sample is clearly seen and some methods, which can be used in certain applications, are suggested.
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- Lindahl, Niklas, 1981
(author)
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Nanoelectromechanical systems from carbon nanotubes and graphene
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Carbon nanotubes and graphene have many interesting properties. To exploit the properties in applications their synthesis and incorporation in devices has to be understood and controlled. This thesis is based on experimental studies on synthesis of carbon nanotubes and fabrication of nanoelectromechanical systems from carbon nanotubes and graphene. Vertically aligned nanotube arrays with heights over 800 µm have been grown using acetylene with iron as catalyst on alumina support using thermal chemical vapor deposition. By varying the partial pressure of acetylene it was found that the addition-rate of carbon was proportional to the coverage of acetylene molecules on the catalyst nanoparticle. In certain conditions the macroscopic pattern of the catalyst areas influenced the microscopic properties of the carbon nanotubes. It was shown that the initial carbon-precursor flow conditions could determine the number of walls produced. The amount of carbon incorporated into nanotubes was constant but regions that experienced less carbon precursor gas flow due e.g. to depletion, produced longer but fewer-walled nanotubes. Arrays of vertically aligned nanotubes were shown to deflect as a single unit under electrostatic actuation, making possible the fabrication of varactors. Measurements of deflection were used to determine an eff ective Young's modulus of 6(+- 4) MPa. The capacitance of such a device could be reproducibly changed by more than 20 %. Devices based on the nanoelectromechanical properties of few-layer graphene were fabricated and characterized. Electrostatic actuation of buckled beams and membranes led to a "snap-through" switching at a critical applied voltage. By characterizing this behavior for diff erent sizes and geometries of membranes, it was possible to extract the bending rigidity of bilayered graphene, yielding a value of 35(+20,-15) eV. CNTFETs with suspended graphene gates were fabricated. It was shown that a moveable graphene gate could control the conductance of the carbon nanotube and improve the switching characteristics. Inverse sub-threshold slope down to 53 mV per decade were measured at 100 K. The experimental data were compared with theoretical simulations and it was inferred that the subthreshold slope could be improved beyond the thermal limit by improving the design of the device.
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