| 1. |
- Acuña, José, 1982-
(författare)
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Distributed thermal response tests : New insights on U-pipe and Coaxial heat exchangers in groundwater-filled boreholes
- 2013
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- U-pipe Borehole Heat Exchangers (BHE) are widely used today in ground source heating and cooling systems in spite of their less than optimal performance. This thesis provides a better understanding on the function of U-pipe BHEs and Investigates alternative methods to reduce the temperature difference between the circulating fluid and the borehole wall, including one thermosyphon and three different types of coaxial BHEs.Field tests are performed using distributed temperature measurements along U-pipe and coaxial heat exchangers installed in groundwater filled boreholes. The measurements are carried out during heat injection thermal response tests and during short heat extraction periods using heat pumps. Temperatures are measured inside the secondary fluid path, in the groundwater, and at the borehole wall. These type of temperature measurements were until now missing.A new method for testing borehole heat exchangers, Distributed Thermal Response Test (DTRT), has been proposed and demonstrated in U-pipe, pipe-in-pipe, and multi-pipe BHE designs. The method allows the quantification of the BHE performance at a local level.The operation of a U-pipe thermosyphon BHE consisting of an insulated down-comer and a larger riser pipe using CO2 as a secondary fluid has been demonstrated in a groundwater filled borehole, 70 m deep. It was found that the CO2 may be sub-cooled at the bottom and that it flows upwards through the riser in liquid state until about 30 m depth, where it starts to evaporate.Various power levels and different volumetric flow rates have been imposed to the tested BHEs and used to calculate local ground thermal conductivities and thermal resistances. The local ground thermal conductivities, preferably evaluated at thermal recovery conditions during DTRTs, were found to vary with depth. Local and effective borehole thermal resistances in most heat exchangers have been calculated, and their differences have been discussed in an effort to suggest better methods for interpretation of data from field tests.Large thermal shunt flow between down- and up-going flow channels was identified in all heat exchanger types, particularly at low volumetric flow rates, except in a multi-pipe BHE having an insulated central pipe where the thermal contact between down- and up-coming fluid was almost eliminated.At relatively high volumetric flow rates, U-pipe BHEs show a nearly even distribution of the heat transfer between the ground and the secondary fluid along the depth. The same applies to all coaxial BHEs as long as the flow travels downwards through the central pipe. In the opposite flow direction, an uneven power distribution was measured in multi-chamber and multi-pipe BHEs.Pipe-in-pipe and multi-pipe coaxial heat exchangers show significantly lower local borehole resistances than U-pipes, ranging in average between 0.015 and 0.040 Km/W. These heat exchangers can significantly decrease the temperature difference between the secondary fluid and the ground and may allow the use of plain water as secondary fluid, an alternative to typical antifreeze aqueous solutions. The latter was demonstrated in a pipe-in-pipe BHE having an effective resistance of about 0.030 Km/W.Forced convection in the groundwater achieved by injecting nitrogen bubbles was found to reduce the local thermal resistance in U-pipe BHEs by about 30% during heat injection conditions. The temperatures inside the groundwater are homogenized while injecting the N2, and no radial temperature gradients are then identified. The fluid to groundwater thermal resistance during forced convection was measured to be 0.036 Km/W. This resistance varied between this value and 0.072 Km/W during natural convection conditions in the groundwater, being highest during heat pump operation at temperatures close to the water density maximum.
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| 2. |
- Ahmed, Ashraf Awadelkarim Widaa, et al.
(författare)
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The Incentives and Challenges of Delivering Linear Broadcasting Services over Cellular Network in Developing Countries : Sudan as Case study
- 2014
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Ingår i: The 25th European Regional Conference of the International Telecommunications Society,Brussels, Belgium, 22nd - 25th June 2014. - Brussels : nternational Telecommunications Society.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Broadcasting sector has been evolved in terms of service production, transmission platform and reception devices in the last few decades. In contrast to cable and satellite platform, which are suitable for fixed reception only, the terrestrial digital platform can support portable, mobile and fixed reception scenarios. In general, there are two options of mobile multimedia service; one is based on a mobile communication network with IP cast known as MBMS (Multimedia Broadcast Multicast Services), while the other is based on broadcast technology. In the context of convergence, the players in the mobile sector argues that unlike traditional mobile network systems, where the use was restricted to a given application, emerging mobile networks will be able to carry a variety of services and accordingly separate broadcasting networks will no longer be required. In line with argument, it is not economically viable to roll out dedicated wireless broadband networks by the broadcasters to meet the increasing demand for interactive broadcasting services. That is why the broadcasters may look for innovative mechanism to deliver the broadcast services over mobile broadband network owned by the telecommunication operators.The focus on this paper is to investigate the incentives and challenges for such trend in developing countries; taking Sudan as case study. The main conclusion in this paper indicate that a potential economic incentive for delivering the broadcasting service over cellular network in Sudan subject to the deployment of high efficient mobile network. Moreover, the mobile operators may consider support such approach considering the increase demand for additional frequency resource. However, the key challenges remain in how to develop a suitable regulations landscape to assure fair and competitive business practices on hand while guaranteeing the continuation of the public broadcasting service. In this regard, a new regulation framework needs to be developed to separate the three key functions in digital terrestrial broadcasting value chain (namely the content production and distribution). Further on, the necessary interconnection regulations need to put on place in order to pave the way for rollout of common platform that are necessary for interactive and nonlinear services.
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| 3. |
- Bergholm, Adam, 1977-
(författare)
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Key Notes on the Unruly City : Social, Material, and Spatial Transgressions
- 2023
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- This research departs from three intersecting field studies in Berlin, Copenhagen, and Paris, and includes both my interventions in the urban texture and integrations with existing communities working in the subject field of the Right to the City (Lefebvre 1968). The projects explore the mutable “nature” of cities and build on political philosophies which describe egalitarian actions that have shaped what those places could be. Laid out across three chapters (X, Y & Z) are descriptions of work processes for multiple projects that locate a social and spatial phenomenon which I call “the unruly city.”Manufactured keys, trapdoors, dug-out tunnels, informal dissemination, bricolaged furniture, loopholes, pulleys, hatches, and shacks recur throughout the thesis; each of these tools, methods or architectural elements support a praxis of transgressivism and stealth. Even if the practical constructions, historical investigations, and cultural theory analyses explored in the thesis do not give access to the physical places themselves, they unlock rooms in the reader’s political imagination, by showing that such spaces exist. At the core of Lefebvre’s philosophical and political argument is the call for action. Praxis is understood here as holding the potential of critical performativity: the possibility to merge culture and politics with claims of creating access to the urban and the production of space. A promise of going beyond philosophy and theory to arrive at praxis. Jacques Rancière (2019) theorizes that which is recognized as (im)possible through sensation. In effect, Rancière addresses a regulation of what can be done. By departing from such an aesthetic order of distributed sensibility, there is the possibility to make a true politics; one which can peel off the foreclosing façades of Western democracy, where the order of things is contested by, as Rancière frames it, the part which has no part. This would be an active politics that challenges the policed order of inclusions and exclusions regarding of what is felt, seen, heard, and perceived. A politics of affect, accomplished by spatial, material, and theoretical practices. In order to imagine the unimaginable—whether it is about spaces, living conditions, or coded systems—imagination must transgress into praxis: speech acts that contributes to our perception, and the other way around. Here, each work becomes a monument to the is-possible—a concrete, non-abstract refutation of any arguments which claim another way of creating or engaging with the city beyond that which is commercially sanctioned to be impossible.
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| 4. |
- Bergman, Svante, et al.
(författare)
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Bit and power loading for spatial multiplexing using partial channel state information
- 2004
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Ingår i: 2004 ITG. - NEW YORK : IEEE. - 0780383273 ; , s. 152-159
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Using information about the channel at the transmitter can improve the performance of Multi-Input Multi-Output (MIMO) communication systems. When perfect Channel State Information (CSI) is available at the transmitter, data can be multiplexed and optimized over independent spatial channels. However, when the available channel information is imperfect or partial, crosstalk between the spatial channels is inevitable, complicating the design of the transmitted data. This paper presents a novel practical bit and power loading algorithm, Spatial Loading based on Incomplete Channel Estimates (SLICE), that enables the use of partial CSI for spatial multiplexing. An approximation for the Bit Error Rate (BER) of the spatial channels is derived that facilitates the loading. Numerical experiments demonstrate performance improvements compared with methods that do not consider the partial information available.
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| 5. |
- Bergquist, Mikael
(författare)
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Josef Frank : Villa Carlsten
- 2019
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Between 1924 and 1936, Austrian-born architect Josef Frank built five holiday homes on the Falsterbo Peninsula in southern Sweden. Conceived as summer houses for friends and relatives of Frank’s Swedish wife, the Falsterbo Villas constitute a key part of Frank’s architectural work and demonstrate concerns at the core of his housing designs. In 2016, Villa Carlsten, the smallest of the Falsterbo houses, underwent an extensive restoration. Published on the occasion of its completion, Josef Frank—Villa Carlsten is the first book to comprehensively document the building. As with all of Frank’s housing designs, Villa Carlsten sees the architect paying special attention to the connection between interior and exterior, to the availability of daylight, and to inhabitants’ movements throughout the building. A particular part of Villa Carlsten’s charm is its scale, as everything is of slightly smaller dimensions than one would expect. Despite its intricate layout, however, Villa Carlsten is also one of Frank’s most accessible homes, and the design is full of wit, combining comfort with modern refinement.Beautifully designed with seventy-five full-color photographs by Mikael Olsson, who adeptly highlights the home’s qualities and relationship with its surroundings, the book also includes an essay by Mikael Bergquist, who realized the renovation and places Villa Carlsten in context with the other Falsterbo Villas and Frank’s broader work.
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| 6. |
- Bergquist, Mikael
(författare)
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Josef Frank Spaces
- 2016. - 1000
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Josef Frank (1885–1967) ranks among Europe’s most significant architects of the twentieth century, and his designs for furniture and textiles have made him one of the eminent figures of modernist interior design. Though there have been many studies of Frank’s architecture previously, Josef Frank—Spaces is the first comprehensive book to look specifically at Frank’s single-family houses.Architects Mikael Bergquist and Olof Michelsen explore the evolution of Frank’s designs for single-family homes over the years, and they investigate the influences that shaped his work, such as Adolf Loos’s “spatial plan” concept, Le Corbusier’s ideas, and Hermann Muthesius’s groundbreaking book The English House. The authors also look at Frank’s architectural concepts of movement and his use of stairs in residential buildings. The book also includes an in-depth examination of six of Frank’s houses, including both built projects—Villas Claeson and Wehtje in Falsterbo, Sweden, and Villa Beer in Vienna—and unrealized ones—House for Vienna XIII, House MS in Los Angeles, and Fantasy House 9 (Accidental House). This section includes images and plans of each of the houses and a close analysis of their specific characteristics. A complete catalog of Frank’s single-family houses rounds out the book.Featuring new material and many previously unpublished images and plans, Josef Frank—Spaces will be the authoritative reference to this renowned architect’s contributions to the design of residential dwellings.
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| 7. |
- Berríos-Negrón, Luis
(författare)
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Anarchives, Site-Specific Greenhouse Superstructures, and Social (Hyperobjective) Pedestals: : the dematerialisation and rematerialisation of colonial memory as environmental form
- 2018
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Ingår i: Black Box: A Record of the Catastrophe, Volume Two. - Oakland, US : PM Press. - 9781629632377
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This paper is about initiating a process of augmentation. The subject of this augmentation is the compound, technical term “greenhouse superstructure”. The process is initiated here by deposing the matter of colonial memory that is entrenched within this term. The deposition takes form as a brief genealogy, an account of related artworks, and a hypothesis about the destabilisation of this technological apparatus. Its passages and components outline the subtle and insidious dialectics of accelerated climate change that are converged and suppressed as an impasse within the very envelop of the term - physically, conceptually, metaphorically. In doing so, I discuss how the discourse, my artworks, and other interventions may reveal, emancipate, and display these entrenched conditions beyond the visual and technological privileges of the “greenhouse”. I thereon argue that these destabilising formats of sculptural display may be referred to as Anarchives, Site-Specific Greenhouse Superstructures, and, ultimately, as Social (Hyperobjective) Pedestals.
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| 8. |
- Berríos-Negrón, Luis, 1971-
(författare)
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Breathtaking Greenhouse Parastructures : a supplement to the Arcades Project from a Caribbean Perspective [and a call for a careful practice of epistemológica].
- 2020
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- Breathtaking Greenhouse Parastructures is a doctoral work that supplements the unfinished modern opus The Arcades Project [in German Das Passagen-Werk (Mit Bindestrich und Werk mit Capital W) ]. The supplement takes the form of a sculptural, historical, and technological deposition of ‘greenhouse’ that presently oscillates between a past-background and future-foreground to Walter Benjamin's ‘theatrical’ handling of the Parisian arcades. From my Caribbean perspective, that oscillating treatment of ‘greenhouse’ affords me a prop from which to activate the following question: is colonial memory the drive of Global Warming? That core question has led me to retrospectively hypothesise that the technology of ‘greenhouse’ is—beyond metaphor—the illusory (dis)embodiment of the toxic binaries of interior & exterior that are still shaping various influential frameworks such as the modern & Marxian ideas of superstructure, as well as the past & future of Western natural sciences (and their histories). Because of that illusory, spectral, if paranormal power, ‘greenhouse’ becomes at once the Western colonial enframing to both the messianic promise for conserving biological history, as well as the messianic remedy to suppress the traumæ that are destining Global Warming. Also, because of that potent (dis)embodied character, the robust analysis of the manifold instrumentalisation of ‘greenhouse’ is set to play a primary role in deposing the geological timeline of the Anthropocene. Now, while the book-supplement is itself the dissertation (as an unpacking of the aforementioned hypothetical findings), the PhD also relies on two other research devices that are worth mentioning: an installation (titled Anarquivo Negantrópico), and an online journal (titled Intransitive Journal). Altogether, the dissertation offers a field from which to asses my broader experimentation with infrastructures, epistemic things, and social pedestals. Moreover, the dissertation revises the so-called forgotten list of ‘Epistemologica’ (the categorical of Western display preparations and phenomenotechnologies) so to format my study and practice into an adaptable, careful, and differentiated kind of epistemológica…a careful study and practice that we may share as object-relations that proportionately (dis)play more-than-human perspectives for (re)mediating the forms and forces of the climate crises.
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| 9. |
- Berríos-Negrón, Luis, 1971-
(författare)
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Earthscore Specularium
- 2018
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Ingår i: On Curating. - Zürich : OnCurating.org. - 2673-2904 .- 2673-2955. ; :36, s. 94-105
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Through an artistic contribution, Luis Berríos-Negrón introduces his project “Earthscore Specularium,” developed at Färg fabriken in Stockholm in 2015. The work of Berríos-Negrón departs from a practice that deals with complexity to reflect upon notions that bring together ecology, art, architecture, science, and social practice. In recent years, he has been developing a set of conceptual devices he ultimately refers to as “social pedestals.” The latter consist of a series of architectonical installations that facilitate social encounters by resolving spatial practicalities, and at the same time reflect conceptually upon the dematerialization of sculpture. The “social pedestal” is conceived as a site for networked agency for social transformation, where the roles of the agents involved can permute, and different configurations can be organized depending of the needs of every specific situation. The “greenhouse”—which Luis treats as a social pedestal itself as well—is a long-term research site of the artist on the possibility of emancipating this type of technology in order to obtain anticipatory spatial, artistic, and social media.
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| 10. |
- 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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