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- Berríos-Negrón, Luis
(författare)
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Greenhouse Doppelgänger Deposed : An Indexical Prototype about Parastructures, Anarchives, and the Social (Hyperobjective) Pedestal
- 2018
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Ingår i: Architecture in Effect: Volume 1: Rethinking the Social in Architecture. - Barcelona : ACTAR. - 9781940291994
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Greenhouse is an opaque manifold of meanings. The opacity is not just the result of a layering that occurs when considering its many definitions. It is more so the result of the suppressed colonial violence that is implicit in its technological instrumentalization. This mythical violence, of willfully transplanting the exotic, is at the heart of allother compound terms and subsets of ‘greenhouse’. I have been working on how this opacity obscures a range of forces that shape the environment. More specifically, I amexploring how these opaque forces affect, and may be perceived through, the forms and languages of sculptural and spatial production beyond prescribed visual or imagined outcomes. The work you will encounter here is then a probe to test how the violent opacity of greenhouse may be demystified by shaping an index as potential format for dematerialized display.
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| 2. |
- Berríos-Negrón, Luis
(författare)
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Tropical Pedagogy : the collapsing interior and exterior of spatial production
- 2016
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Ingår i: The Metropolitan Laboratory. - Berlin, DE : Aedes Network Campus Berlin. - 9783944083032 ; , s. 44-47
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This is a text contribution that briefly explores the political, spatial, and pedagogical dimensions of Tropical Modernism in the Caribbean and Latin America.
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| 3. |
- Khan, Muhammad Sikandar Lal, 1988-
(författare)
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Presence through actions : theories, concepts, and implementations
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During face-to-face meetings, humans use multimodal information, including verbal information, visual information, body language, facial expressions, and other non-verbal gestures. In contrast, during computer-mediated-communication (CMC), humans rely either on mono-modal information such as text-only, voice-only, or video-only or on bi-modal information by using audiovisual modalities such as video teleconferencing. Psychologically, the difference between the two lies in the level of the subjective experience of presence, where people perceive a reduced feeling of presence in the case of CMC. Despite the current advancements in CMC, it is still far from face-to-face communication, especially in terms of the experience of presence.This thesis aims to introduce new concepts, theories, and technologies for presence design where the core is actions for creating presence. Thus, the contribution of the thesis can be divided into a technical contribution and a knowledge contribution. Technically, this thesis details novel technologies for improving presence experience during mediated communication (video teleconferencing). The proposed technologies include action robots (including a telepresence mechatronic robot (TEBoT) and a face robot), embodied control techniques (head orientation modeling and virtual reality headset based collaboration), and face reconstruction/retrieval algorithms. The introduced technologies enable action possibilities and embodied interactions that improve the presence experience between the distantly located participants. The novel setups were put into real experimental scenarios, and the well-known social, spatial, and gaze related problems were analyzed.The developed technologies and the results of the experiments led to the knowledge contribution of this thesis. In terms of knowledge contribution, this thesis presents a more general theoretical conceptual framework for mediated communication technologies. This conceptual framework can guide telepresence researchers toward the development of appropriate technologies for mediated communication applications. Furthermore, this thesis also presents a novel strong concept – presence through actions - that brings in philosophical understandings for developing presence- related technologies. The strong concept - presence through actions is an intermediate-level knowledge that proposes a new way of creating and developing future 'presence artifacts'. Presence- through actions is an action-oriented phenomenological approach to presence that differs from traditional immersive presence approaches that are based (implicitly) on rationalist, internalist views.
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| 4. |
- Sandström, Robin, 1988-
(författare)
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Innovations in nanomaterials for proton exchange membrane fuel cells
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hydrogen technologies are rapidly receiving increased attention as it offers a renewable energy alternative to the current petroleum-based fuel infrastructure, considering that continued large-scale use of such fossil fuels will lead to disastrous impacts on our environment. The proton exchange membrane fuel cell should play a significant role in a hydrogen economy since it enables convenient and direct conversion of hydrogen into electricity, thus allowing the use of hydrogen in applications particularly suited for the transportation industry. To fully realize this, multiple engineering challenges as well as development of advanced nanomaterials must however be addressed.In this thesis, we present discoveries of new innovative nanomaterials for proton exchange membrane fuel cells by targeting the entire membrane electrode assembly. Conceptually, we first propose new fabrication techniques of gas diffusion electrodes based on helical carbon nanofibers, where an enhanced three-phase boundary was noted in particular for hierarchical structures. The cathode catalyst, responsible for facilitating the sluggish oxygen reduction reaction, was further improved by the synthesis of platinum-based nanoparticles with an incorporated secondary metal (iron, yttrium and cobalt). Here, both solvothermal and high-temperature microwave syntheses were employed. Catalytic activities were improved compared to pure platinum and could be attributed to favorably shifted oxygen adsorption energies as a result of successful incorporation of the non-precious metal. As best exemplified by platinum-iron nanoparticles, the oxygen reduction reaction was highly sensitive to both metal composition and the type of crystal structure. Finally, a proton exchange membrane based on fluorine and sulfonic acid functionalized graphene oxide was prepared and tested in hydrogen fuel cell conditions, showing improvements such as lowered hydrogen permeation and better structural stability. Consequently, we have demonstrated that there is room for improvement of multiple components, suggesting that more powerful fuel cells can likely be anticipated in the future.
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| 6. |
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| 7. |
- Dmytryshyn, Andrii, et al.
(författare)
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Canonical structure transitions of system pencils
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We investigate the changes under small perturbations of the canonical structure information for a system pencil (A B C D) − s (E 0 0 0), det(E) ≠ 0, associated with a (generalized) linear time-invariant state-space system. The equivalence class of the pencil is taken with respect to feedback-injection equivalence transformation. The results allow to track possible changes under small perturbations of important linear system characteristics.
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| 8. |
- Hagman, Henrik, 1980-
(författare)
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Co-firing complex biomass in a CFB boiler : ash transformation, corrosion control and materials selection
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The effects of greenhouse gas net emissions on global warming, stricter legislation on waste handling, and the pursuit of ever cheaper heat- and power production are all important factors driving the introduction of complex fuels in incineration plants. However - without fundamental knowledge regarding ash transformation, corrosion control, and materials selection – this introduction of potentially economically and environmentally beneficial fuels, might instead cause economic loss and environmentally adverse effects.The present work is a contribution to the transition from today's CO2 net generating energy conversion system, to a more environmentally friendly and cost-efficient one. This is done using scientific methods to generate knowledge concerning mechanisms of ash transformation, corrosion control, and materials selection, in a co-fired industrial scale circulating fluidized bed (CFB) boiler, using a novel and biomass-based fuel mix, rich in Na, K, Cl, N, S, P, Ca and Si. Fuel fractions, ashes, flue gas, deposits, and construction material samples have been collected and analyzed using various techniques, including scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray Diffraction (XRD). The experimental results have been evaluated and interpreted using chemical equilibrium calculations.The results of this work include:1) An analysis of; the failure and preventive maintenance statistics of the industrial scale CFB boiler at hand; the elemental composition of boiler ashes and deposits, the flue gas composition and elemental composition of a multitude of fuel fractions; correlations between boiler design, operational parameters, elemental composition of deposits and boiler availability; a boiler elemental mass balance revealing details regarding deposit buildup mechanisms; properties of the fly ash relevant to flue gas filter design; and findings regarding the nitrogen chemistry of the novel and nitrogen-rich fuel mix.2) Speciation and description of the overall ash transformation and fireside alloy interaction, enabling the implementation of on-line corrosion control which significantly inhibits superheater and dew-point corrosion in the boiler; and, an equation describing the sulfation potential of the fuel mix, as a result of the direct and indirect interactions between all major ash-forming elements.3) A literature review relevant for the co-fired CFB cyclone vortex finder alloy selection and corrosion at 880 °C; An alloy selection study including long term exposures of several commercially available alloys identifying materials that are more than twice as cost-efficient as the often used alloy 253MA; a suggestion of novel methods for both systematic comparison of heavily degraded alloys, and for alloy service-life estimations; a detailed analysis of heavily degraded alloys 310S, 800H/HT and 600, identifying the driving corrosion mechanisms of the VF alloy degradation, including aspects of how the alloy internal mass transport and fireside surface interaction develops over time.The knowledge gained during this project has been used in the improvement work of the Perstorp 50 MWth CFB boiler, improving the boiler availability with 7 %, reducing the overall energy conversion costs with around 1.7 MEUR/year.
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| 9. |
- Berge, John, 1979, et al.
(författare)
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Design considerations for tunable bulk acoustic wave resonators based on paraelectric phase BaxSr1-xTiO3 thin films
- 2010
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Ingår i: 19th International Symposium on the Applications of Ferroelectrics.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Paraelectric phase BaxSr1-xTiO3 (BSTO) is due to the pronounced field induced piezoelectric effect a promising candidate to realize hysteresis-free tunable thin film bulk acoustic wave resonators (TFBARs) at GHz frequencies. Compared to the conventional fixed-frequency TFBAR technology, mainly based on piezoelectric AlN films, the design of tunable BSTO based resonators require additional considerations due to the demanding conditions necessary for the growth of the BSTO active layer (high temperature, O2 ambient). In this work a number of problems and possible solutions are presented for the specific case of solidly mounted resonators based on an acoustic Bragg reflector structure. Simulation results for a proposed tunable resonator based on a BSTO film and a SiO2/HfO2 reflector stack co-optimized for both longitudinal and shear waves are presented and compared to simulations and existing experimental data from other structures.
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| 10. |
- Ma, Charlie
(författare)
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Aspects of Ash Transformations in Pressurised Entrained-Flow Gasification of Woody Biomass : Pilot-scale studies
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pressurised entrained-flow gasification (PEFG) of woody biomass has the potential to produce high purity syngas for the production of vital chemicals, e.g., biofuels. However, ash-related issues such as reactor blockages and refractory corrosion need to be addressed before this potential can be realised from a technical perspective. These undesirable consequences can be brought about by slag formation involving inorganic ash-forming elements and the chemical transformations that they undergo during fuel conversion. The objective of this study was to elucidate the ash transformations of the major ash-forming elements and the slag formation process. A pilot-scale PEFG reactor was used as the basis of the study, gasifying different woody biomass-based fuels including wood, bark, and a bark/peat mixture. Different ash fractions were collected and chemically analysed. Reactor slags had elemental distributions differing from that of the fuel ash, indicating the occurrence of fractionation of ash material during fuel conversion. Fly ash particles from a bark campaign were also heterogeneous with particles exhibiting differing compositions and physical properties; e.g., molten and crystalline formations. Si was consistently enriched in the reactor slags compared to other major ash-forming elements, while analyses of other ash fractions indicated that K was likely volatilised to a significant extent. In terms of slag behaviour, near-wall temperatures of approximately 1050-1200 °C inside the reactor were insufficient to form flowing ash slag for continuous extraction of ash material during firing the woody biomass fuels alone. However, fuel blending of a bark fuel with a silica-rich peat changed the chemical composition of the reactor slags and bulk slag flow behaviour was evident. Thermochemical equilibrium calculations supported the importance of Si in melt formation and in lowering solidus and liquidus temperatures of Ca-rich slag compositions that are typical from clean wood and bark. Viscosity estimations also showed the impact that solids have upon slag flow behaviour and corresponded qualitatively to the experimental observations. Corrosion of reactor refractory was observed. The mullite-based refractory of the reactor formed a slag with the fuel ash slag, which caused the former to flux away. Reactor blockages were also resultant because of the high viscosity of this slag near the outlet. A preliminary study into the corrosion of different refractories was also carried out, based on firing a bark/peat mixture. Alumina-rich refractories consisting of corundum, hibonite, mullite, and andalusite tended to form anorthite and exhibited varying degrees of degradation. Infiltration of slag was evident for all the samples and was a severe mode of degradation for some refractories. For fused-cast periclase and spinel-based refractories, slag infiltration was limited to voids and no extensive signs of refractory dissolution were found. This is also supported by a thermochemical equilibrium calculations mimicking slag infiltration that incorporated viscosity estimations. The findings from this thesis contribute towards the development of woody biomass PEFG by highlighting issues concerning ash fractionation, slag behaviours and ash\slash refractory interaction that should be investigated further.
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