| 1. |
- Fooladgar, Ehsan, et al.
(författare)
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Low-NOx thermal plasma torches : A renewable heat source for the electrified process industry
- 2024
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Ingår i: Fuel. - : Elsevier Ltd. - 0016-2361 .- 1873-7153. ; 378
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Tidskriftsartikel (refereegranskat)abstract
- Industrial thermal plasma torches can heat a gas up to 5000–20,000 K, i.e., well above the temperature needed to replace the heat generated from the combustion of traditional fossil fuels (e.g., coal, oil, and natural gas) in large-scale process industry furnaces producing construction materials (e.g., iron, steel, lime, and cement). However, there is a risk for significant NOx emissions when air or N2 are used as plasma-forming gas since the temperature somewhere in the furnace always will be higher compared to the threshold NOx formation temperature of ∼1800 K. Torch NOx forms inside the high temperature region of the plasma torch (>5000 K) when air is used as gas. Process NOx forms instead when the hot gas (when air or nitrogen is used as plasma forming gas) from the plasma torch mixes with process air downstream the torch. By analysing the complex chemistry of both the torch- and process NOx formation with thermodynamic equilibrium and one-dimensional chemical kinetic calculations it was shown that adding H2 to the plasma-forming N2 gas significantly reduces the NOx emissions with more than 90 %. Verifying experiments with air, pure N2, and mixtures of H2 and N2 as plasma-forming gas were performed in a laboratory scale insulated laboratory furnace with different pre-heating temperatures of process air (293, 673, and 1073 K) which the plasma gas mixes with downstream the torch. Depending on the pre-heating temperature the NOx emissions were between 12,000–14,000 mg NO2/MJfuel when air was used as plasma forming gas. Substantial NOx emission reduction occurs both when N2 replaces air, where the NOx emissions was in the span of 8000–11,500 mg NO2/MJfuel and furthermore when H2 was mixed into the N2 gas stream. For the highest degree of H2 mixing (28.6 vol-%), the NOx emissions were between 450–1700 mg NO2/MJfuel depending on the pre-heat temperature of the process air, i.e., a reduction of 88–96 % and 85–94 %, respectively when air or N2 was used as plasma forming gas. The measured NOx emissions are then of the same order of magnitude as would be expected from the combustion of traditional fuels (coal, oil, biomass and pure H2). Finally, by analysing the aerodynamics in an axisymmetric furnace with an experimentally validated computational fluid dynamics (CFD) model using reduced chemistry for the NOx formation (19 species and 70 reactions), further guidelines into the process of NOx reduction from thermal plasma torches are given.
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| 2. |
- Fooladgar, Ehsan, et al.
(författare)
-
Low-NOx thermal plasma torches: A renewable heat source for the electrified process industry
- 2024
-
Ingår i: Fuel. - : Elsevier Ltd. - 0016-2361 .- 1873-7153. ; 378
-
Tidskriftsartikel (refereegranskat)abstract
- Industrial thermal plasma torches can heat a gas up to 5000–20,000 K, i.e., well above the temperature needed to replace the heat generated from the combustion of traditional fossil fuels (e.g., coal, oil, and natural gas) in large-scale process industry furnaces producing construction materials (e.g., iron, steel, lime, and cement). However, there is a risk for significant NOx emissions when air or N2 are used as plasma-forming gas since the temperature somewhere in the furnace always will be higher compared to the threshold NOx formation temperature of ∼1800 K. Torch NOx forms inside the high temperature region of the plasma torch (>5000 K) when air is used as gas. Process NOx forms instead when the hot gas (when air or nitrogen is used as plasma forming gas) from the plasma torch mixes with process air downstream the torch. By analysing the complex chemistry of both the torch- and process NOx formation with thermodynamic equilibrium and one-dimensional chemical kinetic calculations it was shown that adding H2 to the plasma-forming N2 gas significantly reduces the NOx emissions with more than 90 %. Verifying experiments with air, pure N2, and mixtures of H2 and N2 as plasma-forming gas were performed in a laboratory scale insulated laboratory furnace with different pre-heating temperatures of process air (293, 673, and 1073 K) which the plasma gas mixes with downstream the torch. Depending on the pre-heating temperature the NOx emissions were between 12,000–14,000 mg NO2/MJfuel when air was used as plasma forming gas. Substantial NOx emission reduction occurs both when N2 replaces air, where the NOx emissions was in the span of 8000–11,500 mg NO2/MJfuel and furthermore when H2 was mixed into the N2 gas stream. For the highest degree of H2 mixing (28.6 vol-%), the NOx emissions were between 450–1700 mg NO2/MJfuel depending on the pre-heat temperature of the process air, i.e., a reduction of 88–96 % and 85–94 %, respectively when air or N2 was used as plasma forming gas. The measured NOx emissions are then of the same order of magnitude as would be expected from the combustion of traditional fuels (coal, oil, biomass and pure H2). Finally, by analysing the aerodynamics in an axisymmetric furnace with an experimentally validated computational fluid dynamics (CFD) model using reduced chemistry for the NOx formation (19 species and 70 reactions), further guidelines into the process of NOx reduction from thermal plasma torches are given.
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| 3. |
- Johansson, Andreas, 1987, et al.
(författare)
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A Simple Experimental Procedure to Determine the Gravitational Acceleration and the Coefficient of Kinetic Friction
- 2024
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Ingår i: 2024 AAPT Winter Meeting.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Classical methods to study kinetic friction are by sliding objects at a constant velocity on a horizontal or inclined plane measuring the pulling force or the inclination angle. These methods require previous knowledge of the value of the gravitational acceleration. The presentation will introduce a laboratory experiment to be used by students at the high school level for simultaneous measurements of gravitational acceleration and the kinetic friction coefficient via video analysis of accelerated and decelerated motion. The simple experiment can be useful for learning aspects of kinetic friction that fall outside of classical models taught in high school and, it can be used to problematize these models in real world situations.
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| 4. |
- Kilde Löfgren, Sebastian, 1991, et al.
(författare)
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Classical mechanics through multiple senses: On using an educational escape room to promote an interest in physics
- 2024
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Ingår i: First International Conference on Embodied Education.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, there has been a rising interest in using escape rooms in education. However, no educational escape rooms focusing on classical mechanics are present in the current literature. Further, as classical mechanics is an area in physics where students bring a plethora of previous embodied knowledge to the classroom, teachers need to aid them in reconciling their bodily experiences with the subject-correct ways of understanding studied phenomena. To this end, the current study explores how an educational escape room situated in an aviation museum can aid upper-secondary physics students in exploring key concepts in classical mechanics through multiple senses in a collaborative, game-based learning setting. Specifically, we ask how students make use of their bodies to make sense of and solve classical mechanics challenges in an educational escape room. We explore this question by conducting a qualitative study involving upper-secondary school classes. Data collected consists of video observations and follow-up semi-structured interviews. Using a physical sense of embodiment, we adhere to the notion that learning and conceptual understanding are grounded in the body. To identify different, increasingly powerful ways of understanding, we conduct a phenomenographic analysis. Using this analytical framework allows us to identify how different embodied practices employed by the students allow for increasingly complex ways of understanding the phenomena faced during the escape room.
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| 5. |
- Bärnarp, Tora, et al.
(författare)
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Skönhet hållbarhet funktion
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna publikation redovisar studenternas enskilda arbeten. Materialet har tillkommit inom ramen för läsårets tema ”Skönhet, hållbarhet och funktion”, men varje studie utgår ifrån studenternas egna val av ämne.
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| 6. |
- Chung, Min Keun, et al.
(författare)
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LuMaMi28 : Real-Time Millimeter-Wave Multi-User MIMO Systems with Antenna Selection
- 2023
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Ingår i: IEEE Transactions on Wireless Communications. - 1536-1276. ; 22:11, s. 7944-7960
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents LuMaMi28, a real-time 28GHz multi-user (MU) multiple-input multiple-output (MIMO) testbed. In this testbed, the base station has 16 transceiver chains with a fully-digital beamforming architecture (with different pre-coding algorithms) and simultaneously supports multiple user equipments (UEs) with spatial multiplexing. The UEs are equipped with a beam-switchable antenna array for real-time antenna selection where the one with the highest channel magnitude, out of four pre-defined beams, is selected. For the beam-switchable antenna array, we consider two kinds of UE antennas, with different beam-width and different peak-gain. Based on this testbed, we provide measurement results for millimeter-wave (mmWave) MU-MIMO performance in different real-life scenarios with static and mobile UEs. We explore the potential benefit of the mmWave MU-MIMO systems with antenna selection based on measured channel data, and discuss the performance results through real-time measurements.
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| 7. |
- Heeger, Thomas, 1993-
(författare)
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Design of Electro-Hydraulic Energy Converters : With Focus on Integrated Designs and Valve Plate Rotation
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In mobile working machines, there is a trend towards replacing combustion engines by electric machines to reduce their carbon footprint. This provides several advantages and challenges for the hydraulic system. The low efficiency of conventional hydraulic systems is no longer acceptable due to the volume and cost of batteries. Luckily, the advantages offered by electrification can be exploited for increased system efficiency. Electrified pump drives (electro-hydraulic energy converters) enable variable speed control, energy recuperation, power-on-demand, and new system architectures with more flexible control. Currently, electro-hydraulic energy converters are typically made by stacking off-the-shelf components. However, off-the-shelf hydraulic machines are not optimized to be combined with electric machines, and thus there is room for improvement. One of these potentials is the volume at the core of electric machines which does not contribute to torque creation. This volume can be used to tightly integrate a hydraulic machine. This tight integration leads to increased power density and the elimination of some parts (e.g., a pair of bearings). This thesis investigates and discusses the design of electro-hydraulic energy converters. Furthermore, this thesis discusses valve plate rotation for a double pump of floating piston type with two valve plates for the following reasons: Firstly, without the noise of the combustion engine, the noise of the hydraulic machine becomes more audible. Valve plate rotation provides variable pre- and de-compression, and is therefore investigated to reduce fluid-borne noise. Secondly, electric machines can be overloaded for some time. In order to protect them from overheating when maximum pressure is demanded continuously, the torque load can be reduced by reducing the hydraulic machine’s displacement. Conventional swash-plate tilting needs significant leakage to be stable, which reduces the efficiency. Valve plate rotation requires low control power and could therefore increase efficiency, and is thus investigated in this thesis. However, valve plate rotation remains challenging for the following reasons: For low displacement setting ratios, the axial speed of the pistons at commutation is increased, increasing the throttling effect. Also, the hydrostatic forces acting on the valve plate change when rotating the valve plate.
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| 8. |
- Johansson, Andreas
(författare)
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Deliberating Intractability : Exploring Prospects of Deliberative Democracy in Intractable Natural Resource Management Conflicts
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing prevalence of intractable conflicts over natural resources, which defy technocratic solutions, highlights an urgent need for states, managers, and practitioners to find democratic methods for addressing them. In the normative debate over the optimal approach to managing these conflicts, deliberative democracy has emerged as a leading theoretical framework, sparking a deliberative turn in both political theory and natural resource governance. While the normative value of deliberative democracy—where the public collaboratively shapes collective decisions through reasoned discourse under conditions of equality and fairness—is widely acknowledged, its practical effectiveness in addressing intractable natural resource conflicts, particularly its capacity to foster productive reframing outcomes conducive to legitimate decisions or agreements, remains uncertain. In response to these uncertainties, this thesis explores the potential of deliberative democracy in intractable natural resource conflicts, using Swedish mining governance and its associated intractable conflicts as the empirical setting. It employs a qualitative case study design rooted in an interpretive analytical paradigm to investigate the possibility of achieving deliberation and associated reframing outcomes among disputing actors, examine the extent to which and how the ideal of deliberative democracy has manifested within the governance system entwined with the conflicts, and explore the interplay between contextual factors, deliberation, and associated reframing outcomes.The thesis concludes that while achieving consensus or mutually accepted agreement through deliberation in intractable conflicts may be unlikely, it is possible, given strict adherence to deliberative design principles and significant contextual knowledge, to realize ideal deliberation and the outcome of meta-consensus. This outcome holds substantial value as it can transform intractable conflicts into structured and respectful disagreements, thereby clarifying the conflicts and their dividing lines. Consequently, it makes intractable situations more manageable, facilitating efforts to reach compromises when feasible and make trade-offs when they are not. Furthermore, the thesis shows that meta-consensus can endure amid ongoing conflict and heightened polarization. However, the thesis also concludes that ideal deliberation and meta-consensus may not be attainable in all conflict scenarios due to contextual barriers. Factors, including strained pre-conflict community relations rooted in historical state decisions, a lack of prior foundation for inter-group engagement, entrenched affiliations among participants, and obstacles within the institutional design of the governance system, were identified as impediments to the realization of ideal deliberation and its associated outcomes. The thesis also reaffirms the challenges of extending deliberative democracy beyond isolated forums to pre-existing governance systems. Notably, while the investigated governance system has demonstrated an increasing commitment to deliberative norms and practices, a discernible gap exists between the system's current state and the principles of deliberative democracy, suggesting a "business as usual" scenario rather than a transition toward a deliberative democratic governance system.In light of these findings, this thesis provides several suggestions for aligning the system and other comparable governance systems with the deliberative democratic norms they aspire to achieve. It also proposes several directions for future research. These include exploring how deliberative processes can be optimally tailored to meet the unique demands of different contexts, continuing efforts to identify and address institutional and other contextual enablers and barriers to deliberation at both the micro and system levels. Addressing system-level barriers is particularly important if deliberation is to flourish beyond isolated forums. Furthermore, recognizing that meta-consensus does not provide a direct resolution to conflicts and cannot be enabled under all conditions, it is essential to identify mechanisms for trade-offs or outcomes that are deemed fair and acceptable even by those who do not get their preferences realized. Additionally, acknowledging the possibility of harnessing long-term democratization effects of conflicts, more research to determine when and under what conditions conflicts and various non-democratic actions yield positive effects is crucial.
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| 9. |
- Johansson, Andreas
(författare)
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Managing Intractable Natural Resource Conflicts: Exploring Possibilities and Conditions for Reframing in a Mine Establishment Conflict in Northern Sweden
- 2023
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Ingår i: Environmental Management. - : Springer Nature. - 0364-152X .- 1432-1009. ; 72:4, s. 818-837
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Tidskriftsartikel (refereegranskat)abstract
- Natural resource management (NRM) increasingly relies on communicative measures to enable reframing in intractable conflicts. Reframing occurs when disputants change their perceptions of a conflict situation, and/or their preferences for dealing with it. However, the types of reframing possible, and the conditions under which they can occur, remain unclear. Through an inductive and longitudinal analysis of a mine establishment conflict in northern Sweden this paper explores to what extent, how, and under what conditions reframing can occur in intractable NRM conflicts. The findings reveal the difficulty in achieving consensus-oriented reframing. Despite multiple dispute resolution efforts, the disputants’ perceptions and preferences became increasingly polarized. Nonetheless, the results suggest that it is possible to enable reframing to the extent that all disputants can understand and accept each other’s different perceptions and positions, i.e., meta-consensus. Meta-consensus hinges on neutral, inclusive, equal, and deliberative intergroup communication. However, the results show that intergroup communication and reframing are significantly informed by institutional and other contextual factors. For example, when implemented within the formal governance system in the investigated case, intergroup communication lagged in quality and did not contribute to meta-consensus. Moreover, the results show that reframing is strongly influenced by the nature of the disputed issues, actors’ group commitments, and the governance system’s distribution of power to the actors. Based on these findings, it is argued that more efforts should focus on how governance systems can be configurated so that high-quality intergroup communication and meta-consensus can be enabled and inform decision making in intractable NRM conflicts.
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| 10. |
- Bujosa Mateu, Daniel, et al.
(författare)
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The Effects of Clock Synchronization in TSN Networks with Legacy End-Stations
- 2022
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present our ongoing work on proposing solutions to integrate legacy end-stations into Time-Sensitive Network (TSN) communication systems where the legacy end-stations are synchronized via their legacy clock synchronization protocol. To this end, we experimentally identify the effects of lacking synchronization or partial synchronization in TSN networks. In the experiments we show the effects of clock synchronization in different scenarios on jitter and clock drifts. Based on the experiments, we propose preliminary solutions to overcome the identified effects.
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