| 1. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Investigation of the Behavior of Alkali Chlorides during Sulfur Recirculation in a Waste-to-Energy Facility
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- High temperature corrosion related issues are known problems for Waste-to-Energy facilities where the formation of alkali chlorides is among the most problematic species formed during the combustion. Sulfur Recirculation is a novel technology developed to reduce the chlorine content in the ash and in that way also the corrosivity of the ash. This concept has been installed at the Maabjerg Energy Center (MEC) in Denmark. This work aims to take a first step towards a reaction kinetics based model that can describe systems like the MEC boiler and to evaluate the impact of Sulfur Recirculation. This is done by implementing a plug flow reactor model in the software Chemkin. Previously obtained data from on-site experiments and CFD simulations is used as input to the model. The model is focused on describing the sulfation of alkali chlorides and the result from the model is compared to experiments. The model is able to predict the degree of sulfation with less than 10% deviation from the experimental results. Both the experiment and the model show a clear benefit from implementing sulfur recirculation which lowers the chlorine content in the up to as much as 70%. It is, however, also shown that the results are sensitive towards several of the assumptions made. Even though there is a relatively good agreement in final sulfation between model and experiments the model is not able to represent the detailed chemistry in a realistic way in its current state; further development is required.
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| 2. |
- Andersson, Lisa, et al.
(författare)
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Mutations in DMRT3 affect locomotion in horses and spinal circuit function in mice
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 488:7413, s. 642-646
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Tidskriftsartikel (refereegranskat)abstract
- Locomotion in mammals relies on a central pattern-generating circuitry of spinal interneurons established during development that coordinates limb movement(1). These networks produce left-right alternation of limbs as well as coordinated activation of flexor and extensor muscles(2). Here we show that a premature stop codon in the DMRT3 gene has a major effect on the pattern of locomotion in horses. The mutation is permissive for the ability to perform alternate gaits and has a favourable effect on harness racing performance. Examination of wild-type and Dmrt3-null mice demonstrates that Dmrt3 is expressed in the dI6 subdivision of spinal cord neurons, takes part in neuronal specification within this subdivision, and is critical for the normal development of a coordinated locomotor network controlling limb movements. Our discovery positions Dmrt3 in a pivotal role for configuring the spinal circuits controlling stride in vertebrates. The DMRT3 mutation has had a major effect on the diversification of the domestic horse, as the altered gait characteristics of a number of breeds apparently require this mutation.
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| 3. |
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| 4. |
- Eriksson, Lars-Erik, 1950, et al.
(författare)
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Development of a Cooled Radial Flameholder for the F404/RM12 Afterburner: Part III Afterburner Rumble Prediction and Suppression
- 2003
-
Ingår i: ISABE-2003-1060, proc. of 16th ISABE Conf, Cleveland Ohio, September 2003.
-
Konferensbidrag (refereegranskat)abstract
- One-dimensional methods used for solving acoustic instabilities are of doubtful value in the design of afterburner systems. In this paper a three-dimensional method developed and used at Volvo Aero Corporation is described. The method deals with the mean flow and the perturbation flow separately. The perturbation part is based on the linearized Euler equations (time domain) for compressible multi-species flow together with a spectrum trans-formation and Arnoldis method for eigenmode extraction.
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| 5. |
- Gäre, Klas, 1948-, et al.
(författare)
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Evidence informed healthcare improvement : Design and evaluation
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Healthcare is in constant change with fast development in knowledge, new technology and varying needs and expectations from patients, citizens, management, and politicians. There is a challenge in balancing the involved actors´ focus, needs, preferences, and resources for healthcare improvement. Improvement of healthcare is an ongoing activity, sometimes managed and controlled, often not. A key ingredient for success is competence where the need for competence varies with perspectives of the improving actors. Actors in healthcare improvement are professionals, patients, politicians, management, citizens, researchers, research foundations and others. In this report a review of frameworks in healthcare improvement are presented together with management myths and questions around needs for healthcare improvement competence and capabilities currently on the agenda.Most improvement initiatives of some size have substantial parts of IT and have had so for a considerable time. This rather long experience of more and less successful IT implementation and use is transparent and useful in all kinds of healthcare improvement. One important issue in this report is what has real impact is the actual understanding and use of innovations and artefacts by healthcare actors in a broad sense for healthcare improvement (e.g., new clinical evidence, clinical guidelines, process changes, information systems and more). The aim in this report is to review frameworks which can be useful in healthcare improvement as well as in the study of healthcare improvement.Conclusions concern what is found to be important to study and understand healthcare improvement, considering the presented frameworks. Improvement of healthcare is present in all the frameworks but in different ways and what is emphasized concerning scope and focus. Improving healthcare take place in the interaction of at least two parts, one of which is healthcare professionals, and another is the patient/next-of-kin. Professionals and patient populations interact in processes of social networks and structures. Actors and context are useful concepts for understanding action (use) and its social contexts. The actual use of innovations is best understood in terms of integration into clinical activities and processes – actors’ interaction, coordination and communication activities and processes.Theoretical implications are that there is a need for more research concerning meso and macro perspectives on methods for healthcare improvement, and the interplay of perspectives regarding the understanding of improvement in healthcare. Of course, a challenge is that the objects of improvement are complex adaptive systems of healthcare is not easily to catch in simple rules. They are genuinely difficult both to change and evaluate changes. Practical implications of the report support design and contents of education programs in improvement of healthcare, in better understanding usefulness, practice, use, and experience base. To help the understanding of the need and usefulness of integrating different perspectives for successful healthcare improvement, e.g., micro, meso, and macro perspectives, use of mixed methods and more.
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| 6. |
- H. Moud, Pouya, et al.
(författare)
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Biomass pyrolysis gas conditioning over an iron-based catalyst for mild deoxygenation and hydrogen production
- 2017
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 211, s. 149-158
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Bio-crude is a renewable source for production of valuable energy carriers. Prior to its utilization, a conditioning step of the raw pyrolysis gas can be beneficial before the bio-crude is converted via catalytic hydrodeoxygenation (HDO) into liquid hydrocarbon products, or via steam reforming (SR) to synthesis gas/hydrogen. An experimental small industrial scale study for the chemistry of atmospheric pressure pyrolysis gas conditioning resulting in bio-crude deoxygenation and a hydrogen-rich gas using an iron-based catalyst without addition of hydrogen or steam is presented and discussed. Following a short catalyst stabilization period with fluctuating bed temperatures, the catalyst operated near 450°C at a space velocity of 1100 h-1 for 8 hours under stable conditions during which no significant catalyst deactivation was observed. Experimental results indicate a 70-80% reduction of acetic acid, methoxy phenols, and catechol, and a 55-65% reduction in non-aromatic ketones, BTX, and heterocycles. Alkyl phenols and phenols were least affected, showing a 30-35% reduction. Conditioning of the pyrolysis gas resulted in a 56 % and a 18 wt% increase in water and permanent (dry) gas yield, respectively, and a 29 % loss of condensable carbon. A significant reduction of CO amount (-38 %), and production of H2 (+1063 %) and CO2 (+36 %) over the catalyst was achieved, while there was no or minimal change in light hydrocarbon content. Probing the catalyst after the test, the bulk phase of the catalyst was found to be magnetite (Fe3O4) and the catalyst exhibited significant water gas shift (WGS) reaction activity. The measured gas composition during the test was indicative of no or very limited Fischer-Tropsch (FT) CO /CO2 hydrogenation activity and this infers that also the active surface phase of the catalyst during the test was Fe-oxide, rather than Fe-carbide. The results show that iron-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way of generating a hydrogen-enriched gas without the need for bio-crude condensation.
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| 7. |
- H. Moud, Pouya
(författare)
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Catalytic Conversion of Undesired Organic Compounds to Syngas in Biomass Gasification and Pyrolysis Applications
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reliable energy supply is a major concern and crucial for development of the global society. To address the dependency on fossil fuel and the negative effects of this reliance on climate, there is a need for a transition to cleaner sources. An attractive solution for replacing fossil-based products is renewable substitutes produced from biomass. Gasification and pyrolysis are two promising thermochemical conversion technologies, facing challenges before large-scale commercialization becomes viable. In case of biomass gasification, tar is often and undesired by-product. An attractive option to convert tar into syngas is nickel-based catalytic steam reforming (SR). For biomass pyrolysis, catalytic SR is in early stages of investigation as a feasible option for bio-crude conversion to syngas.The focus of the thesis is partly dedicated to describe research aimed at increasing the knowledge around tar reforming mechanisms and effect of biomass-derived impurities on Ni-based tar reforming catalyst downstream of gasifiers. The work focuses on better understanding of gas-phase alkali interaction with Ni-based catalyst surface under realistic conditions. A methodology was successfully developed to enable controlled investigation of the combined sulfur (S) and potassium (K) interaction with the catalyst. The most striking result was that K appears to lower the sulfur coverage and increases methane and tar reforming activity. Additionally, the results obtained in the atomistic investigations are discussed in terms of naphthalene adsorption, dehydrogenation and carbon passivation of nickel.Furthermore, the thesis describes research performed on pyrolysis gas pre-conditioning at a small-industrial scale, using an iron-based catalyst. Findings showed that Fe-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way for generating a hydrogen-enriched gas without the need for bio-crude condensation.
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| 8. |
- Haghighi Moud, Pouya, et al.
(författare)
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Equilibrium potassium coverage and its effect on a Ni tar reforming catalyst in alkali- and sulfur-laden biomass gasification gases
- 2016
-
Ingår i: Applied Catalysis B. - : Elsevier. - 0926-3373 .- 1873-3883. ; 190, s. 137-146
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Tidskriftsartikel (refereegranskat)abstract
- Biomass conversion to syngas via gasification produces certain levels of gaseous by-products, such as tar and inorganic impurities (sulfur, potassium, phosphorus etc.). Nickel, a commonly used catalyst for hydrocarbqn steam reforming, suffers reduced reforming activity by small amounts of sulfur (S) or potassium (K), while resistance against deleterious carbon whisker formation increases. Nevertheless, the combined effect of biomass derived gas phase alkali at varying concentrations together with sulfur on tar reforming catalyst performance under realistic steady-state conditions is largely unknown. Prior to this study, a methodology to monitor these effects by precise K dosing as well as K co-dosing with S was successfully developed. A setup consisting of a 5 kW biomass fed atmospheric bubbling fluidized bed gasifier, a high temperature hot gas ceramic filter, and a catalytic reactor operating at 800 degrees C were used in the experiments. Within the current study, two test periods were conducted, including 30 h with 1 ppmv potassium chloride (KCl) dosing followed by 6 h without KCl dosing. Besides an essentially carbon-free operation, it can be concluded that although K, above a certain threshold surface concentration, is known to block active Ni sites and decrease activity in traditional steam reforming, it appears to lower the surface S coverage (theta(s)) at active Ni sites. This reduction in theta(s) increases the conversion of methane and aromatics in tar reforming application, which is most likely related to K-induced softening of the S-Ni bond. The K-modified support surface may also contribute to the significant increase in reactivity towards tar molecules. In addition, previously unknown relevant concentrations of K during realistic operating conditions on typical Ni-based reforming catalysts are extrapolated to lie below 100 mu K/m(2), a conclusion based on the 10-40 mu K/m(2) equilibrium coverages observed for the Ni/MgAl2O4 catalyst in the present study.
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| 9. |
- Hernandez, Asbel, et al.
(författare)
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Gas-Phase Potassium Effects and the Role of the Support on the Tar Reforming of Biomass-Derived Producer Gas Over Sulfur-Equilibrated Ni/MgAl2O4
- 2020
-
Ingår i: Energy & Fuels. - : American Chemical Society. - 0887-0624 .- 1520-5029. ; 34:9, s. 11103-11111
-
Tidskriftsartikel (refereegranskat)abstract
- Biomass gasification is a sustainable way to convert biomass residues into valuable fuels and chemicals via syngas production. However, several gas impurities need to be removed before the final synthesis. Understanding of the interactions and effects of biomass-derived producer gas contaminants (S and K) on the performance of reforming catalysts is of great importance when it comes to process reliability and development. In the present study, the steam reforming activity at 800 °C of a sulfur-equilibrated nickel catalyst during controlled exposure to alkali species (∼2 ppmv K) and in its absence was investigated using real producer gas from a 5 kWth O2-blown fluidized-bed gasifier. Conversions of CH4, C2H4, and C10H8 were used to evaluate the performance of the Ni/MgAl2O4 catalyst and MgAl2O4 support. A significant and positive effect on the catalyst activity is observed with addition of gas-phase KCl. This is assigned primarily to the observed K-induced reduction in sulfur coverage (θS) on Ni—an effect which is reversible. The catalytic contribution of the K-modified pure MgAl2O4 support was found to be significant in the conversion of naphthalene but not for light hydrocarbons. The product and catalyst analyses provided evidence to elucidate the preferential adsorption site for S and K on the catalyst as well as the role of the support. Whereas S, as expected, was found to preferentially adsorb on the surface of Ni particles, forming S-Ni sites, K was found to preferentially adsorb on the MgAl2O4 support. A low but still significant K adsorption on S–Ni sites, or an effect on only the fraction of exposed Ni surface area near the metal–support interface, can, however, not be excluded. The result suggests that an improved Ni/MgAl2O4 catalyst activity and an essentially carbon-free operation can be achieved in the presence of controlled amount of gas-phase potassium and high sulfur coverages on Ni. Based on the results, a mechanism of the possible K–S interactions is proposed.
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| 10. |
- Hernandez, Asbel, et al.
(författare)
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Preferential adsorption of K species and the role of support during reforming of biomass derived producer gas over sulfur passivated Ni/MgAl2O4
- 2020
-
Ingår i: Energy & Fuels. - 0887-0624 .- 1520-5029. ; 34:9, s. 11103-11111
-
Tidskriftsartikel (refereegranskat)abstract
- Biomass gasification is a sustainable way to convert biomass residues into valuable fuels and chemicals via syngasproduction. However, several gas impurities need to be removed before thefinal synthesis. Understanding of the interactions andeffects of biomass-derived producer gas contaminants (S and K) on the performance of reforming catalysts is of great importancewhen it comes to process reliability and development. In the present study, the steam reforming activity at 800°C of a sulfur-equilibrated nickel catalyst during controlled exposure to alkali species (∼2 ppmv K) and in its absence was investigated using realproducer gas from a 5 kWthO2-blownfluidized-bed gasifier. Conversions of CH4,C2H4, and C10H8were used to evaluate theperformance of the Ni/MgAl2O4catalyst and MgAl2O4support. A significant and positive effect on the catalyst activity is observedwith addition of gas-phase KCl. This is assigned primarily to the observed K-induced reduction in sulfur coverage (θS)onNianeffect which is reversible. The catalytic contribution of the K-modified pure MgAl2O4support was found to be significant in theconversion of naphthalene but not for light hydrocarbons. The product and catalyst analyses provided evidence to elucidate thepreferential adsorption site for S and K on the catalyst as well as the role of the support. Whereas S, as expected, was found topreferentially adsorb on the surface of Ni particles, forming S-Ni sites, K was found to preferentially adsorb on the MgAl2O4support.A low but still significant K adsorption on S−Ni sites, or an effect on only the fraction of exposed Ni surface area near the metal−support interface, can, however, not be excluded. The result suggests that an improved Ni/MgAl2O4catalyst activity and anessentially carbon-free operation can be achieved in the presence of controlled amount of gas-phase potassium and high sulfurcoverages on Ni. Based on the results, a mechanism of the possible K−S interactions is proposed
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| 11. |
- Markljung, Ellen, et al.
(författare)
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ZBED6, a novel transcription factor derived from a domesticated DNA transposon regulates IGF2 expression and muscle growth
- 2009
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Ingår i: PLoS biology. - : Public Library of Science (PLoS). - 1544-9173 .- 1545-7885. ; 7:12, s. e1000256-
-
Tidskriftsartikel (refereegranskat)abstract
- A single nucleotide substitution in intron 3 of IGF2 in pigs abrogates a binding site for a repressor and leads to a 3-fold up-regulation of IGF2 in skeletal muscle. The mutation has major effects on muscle growth, size of the heart, and fat deposition. Here, we have identified the repressor and find that the protein, named ZBED6, is previously unknown, specific for placental mammals, and derived from an exapted DNA transposon. Silencing of Zbed6 in mouse C2C12 myoblasts affected Igf2 expression, cell proliferation, wound healing, and myotube formation. Chromatin immunoprecipitation (ChIP) sequencing using C2C12 cells identified about 2,500 ZBED6 binding sites in the genome, and the deduced consensus motif gave a perfect match with the established binding site in Igf2. Genes associated with ZBED6 binding sites showed a highly significant enrichment for certain Gene Ontology classifications, including development and transcriptional regulation. The phenotypic effects in mutant pigs and ZBED6-silenced C2C12 myoblasts, the extreme sequence conservation, its nucleolar localization, the broad tissue distribution, and the many target genes with essential biological functions suggest that ZBED6 is an important transcription factor in placental mammals, affecting development, cell proliferation, and growth.
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| 12. |
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| 13. |
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| 14. |
- Musa, Najihah, et al.
(författare)
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Using Sex Pheromone and a Multi-Scale Approach to Predict the Distribution of a Rare Saproxylic Beetle
- 2013
-
Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 8:6
-
Tidskriftsartikel (refereegranskat)abstract
- The European red click beetle, Elater ferrugineus L., is associated with wood mould in old hollow deciduous trees. As a result of severe habitat fragmentation caused by human disturbance, it is threatened throughout its distribution range. A new pheromone-based survey method, which is very efficient in detecting the species, was used in the present study to relate the occurrence of E. ferrugineus to the density of deciduous trees. The latter data were from a recently completed regional survey in SE Sweden recording >120,000 deciduous trees. The occurrence of E. ferrugineus increased with increasing amount of large hollow and large non-hollow trees in the surrounding landscape. Quercus robur (oak) was found to be the most important substrate for E. ferrugineus, whereas two groups of tree species (Carpinus betulus, Fagus sylvatica, Ulmus glabra, vs. Acer platanoides, Aesculus hippocastanum, Fraxinus excelsior, Tilia cordata) were less important but may be a complement to oak in sustaining populations of the beetle. The occurrence of E. ferrugineus was explained by the density of oaks at two different spatial scales, within the circle radii 327 m and 4658 m. In conclusion, priority should be given to oaks in conservation management of E. ferrugineus, and then to the deciduous trees in the genera listed above. Conservation planning at large spatial and temporal scales appears to be essential for long-term persistence of E. ferrugineus. We also show that occurrence models based on strategic sampling might result in pessimistic predictions. This study demonstrates how pheromone-based monitoring make insects excellent tools for sustained feedback to models for landscape conservation management.
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| 15. |
- Nordin, Steven, et al.
(författare)
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Impact of Health-Risk Perception on Odor Perception and Cognitive Performance
- 2013
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Ingår i: Chemosensory Perception. - : Springer Science and Business Media LLC. - 1936-5802 .- 1936-5810. ; 6:4, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- Indications of adverse effects of nontoxic malodorous chemical exposure on work performance and safety and the role of health-risk perception on odor perception motivated the present study of the impact of health-risk perception on odor perception and cognitive performance. Healthy young adults were informed that they were to be exposed to an odorous substance that is either potentially health-enhancing (positive information bias, n = 24) or hazardous (negative information bias, n = 25). The two groups, screened for loss in odor-detection sensitivity, were matched for age, sex, chemical intolerance, and negative affectivity. During each of 14 trials of exposure to 433 mg/m(3) of n-butanol, the participants rated the intensity and valence of odor perception and performed a cognitive task that taxed working memory and attention. The results showed that the negative-bias group rated the odor perception as more unpleasant than did the positive-bias group during the entire session, but significantly more unpleasant only during the first half of the session. The negative-bias group was also found to perform significantly poorer on the cognitive task during both halves of the session. No effect of information bias was found on perceived odor intensity. The results provide experimental support for the hypotheses that belief that exposure to an odorous chemical is hazardous contributes to the odor perception being more unpleasant and to poorer cognitive performance.
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| 16. |
- Prasad, Ankur, 1987, et al.
(författare)
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Symmetrical modeling of GaN HEMTS
- 2014
-
Ingår i: Technical Digest - IEEE Compound Semiconductor Integrated Circuit Symposium, CSIC. - 1550-8781. - 9781479936229
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a symmetrical small signal model for GaN HEMTs valid for both positive and negative Vds. The model takes advantage of the intrinsic symmetry of the devices typically used for switches. The parameters of the model are extracted using a new symmetrical optimization based extraction method, optimizing simultaneously for both positive and negative drain-source bias points. This ensures a symmetrical small signal model with lower modeling error. The small signal model can be further used to simplify the development of a large-signal model. The small signal model is validated with measured S- parameters of a commercial GaN HEMT.
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| 17. |
- Wallén-Mackenzie, Åsa, et al.
(författare)
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Restricted cortical and amygdaloid removal of vesicular glutamate transporter 2 in preadolescent mice impacts dopaminergic activity and neuronal circuitry of higher brain function.
- 2009
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Ingår i: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401 .- 0270-6474. ; 29:7, s. 2238-51
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Tidskriftsartikel (refereegranskat)abstract
- A major challenge in neuroscience is to resolve the connection between gene functionality, neuronal circuits, and behavior. Most, if not all, neuronal circuits of the adult brain contain a glutamatergic component, the nature of which has been difficult to assess because of the vast cellular abundance of glutamate. In this study, we wanted to determine the role of a restricted subpopulation of glutamatergic neurons within the forebrain, the Vglut2-expressing neurons, in neuronal circuitry of higher brain function. Vglut2 expression was selectively deleted in the cortex, hippocampus, and amygdala of preadolescent mice, which resulted in increased locomotor activity, altered social dominance and risk assessment, decreased sensorimotor gating, and impaired long-term spatial memory. Presynaptic VGLUT2-positive terminals were lost in the cortex, striatum, nucleus accumbens, and hippocampus, and a downstream effect on dopamine binding site availability in the striatum was evident. A connection between the induced late-onset, chronic reduction of glutamatergic neurotransmission and dopamine signaling within the circuitry was further substantiated by a partial attenuation of the deficits in sensorimotor gating by the dopamine-stabilizing antipsychotic drug aripiprazole and an increased sensitivity to amphetamine. Somewhat surprisingly, given the restricted expression of Vglut2 in regions responsible for higher brain function, our analyses show that VGLUT2-mediated neurotransmission is required for certain aspects of cognitive, emotional, and social behavior. The present study provides support for the existence of a neurocircuitry that connects changes in VGLUT2-mediated neurotransmission to alterations in the dopaminergic system with schizophrenia-like behavioral deficits as a major outcome.
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| 18. |
- Ajdari, Sima, 1985, et al.
(författare)
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Evaluation of Operating and Design Parameters of Pressurized Flue Gas Systems with Integrated Removal of NO x and so x
- 2019
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 33:4, s. 3339-3348
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the operating and design parameters of product gas compression and integrated control of nitrogen oxides (NO x ) and sulfur oxides (SO x ) in large-scale oxy-fuel and chemical looping combustion processes. A process model that includes a comprehensive description of nitrogen and sulfur chemistry and mass transfer is developed. The results show that the fraction of NO oxidation into NO 2 will be 10-50% in a multistage compressor to 30 bars (1-4% O 2 in the gas) depending on the residence times in intercoolers and pressure levels. At lower O 2 concentrations (>0.1% O 2 in the gas), the oxidation is limited but still active. Nitric acid formation in the compressor condensate is, thus, inevitable, although limited, as most water is condensed in the early stages, whereas the acid gases are formed in the later stages. The NO 2 /NO x ratio has an important effect on the total amount of NO x absorbed and extra residence time should be added after the compressor to increase this ratio. Evaluation of the process behavior in relation to simultaneous absorption of SO 2 and NO x revealed that increased SO 2 /NO x ratio and bottom liquid recycling enhanced the total NO x absorption. In addition, maintaining the pH in the absorbing solution above 5 improves the removal efficiencies of NO x and SO 2 . NO x removal rates of up to around 95% can be achieved for SO 2 /NO x > 1 in the flue gas with appropriate design of the absorber. For SO 2 /NO x < 1, increasing the packing height or addition of S(IV) solutions could enhance the NO x removal rates to 95% or more. The model predictions are compared with the experimental data from a laboratory-scale absorber. The process model developed in this work enables design studies and techno-economic evaluation of absorption-based NO x and SO x removal concepts.
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| 19. |
- Ajdari, Sima, 1985, et al.
(författare)
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Formation and Control of NOx and SOx in Pressurized Oxy-Combustion Systems
- 2015
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Ingår i: The Proceedings of the 40th International Technical Conference on Clean Coal & Fuel Systems, 31 May-4 June 2015, Clearwater, Florida, USA.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The formation and control of NOx and SOx in pressurized oxy-fuel combustion systems is discussed in the present work. The chemistry of nitrogen and sulfur species under pressurized conditions and the experiences gained from operating atmospheric oxy-fuel combustion pilot plants are reviewed in brief. In a conventional combustion and gas cleaning process, SO2 and NO are the principle NOx and SOx species. However, the oxidation of NO to NO2 and SO2 to SO3 is favored by low temperature and high pressure. In the present paper we will make a first modelling based of the altered oxidation conditions during both high and low temperature conditions in pressurized oxy-combustion. Besides the gas-phase oxidation, the liquid-phase N-S interactions will further enhance the formation of acids in the flue gas condensate. Thus, these low and high temperature processes will be discussed in the present work due to their relevance for the design of the flue gas compression and gas cleaning system in pressurized oxy-combustion.
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| 20. |
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| 21. |
- Ajdari, Sima, 1985, et al.
(författare)
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Modeling the Nitrogen and Sulfur Chemistry in Pressurized Flue Gas Systems
- 2015
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 54:4, s. 1216-1227
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Tidskriftsartikel (refereegranskat)abstract
- A rate-based model is developed to elucidate the chemistry behind the simultaneous absorption of NOx and SOx under pressurized conditions (pressures up to 30 bar) that are applicable to the flue gases obtained from CO2 capture systems. The studied flue gas conditions are relevant to oxy-fuel and chemical-looping combustion systems. The kinetics of the reactions implemented in the model is based on a thorough review of the literature. The chemistry of nitrogen, sulfur, and N-S interactions are evaluated in detail, and the most important reaction pathways are discussed. The effects of pH, pressure, and flue-gas composition on the liquid-phase chemistry are also examined and discussed. Simulations that use existing kinetic data reveal that the pH level has a strong influence on the reaction pathway that is followed and the types of products that are formed in the liquid phase. In addition, the pressure level and the presence of NOx significantly affect the removal of SO2 from the flue gas.
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| 22. |
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| 23. |
- Ajdari, Sima, 1985, et al.
(författare)
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NOx AND SOx CHEMISTRY IN PRESSURIZED FLUE GAS SYSTEMS: IMPORTANCE FOR CHEMICAL LOOPING COMBUSTION
- 2014
-
Ingår i: 3rd International Conference on Chemical Looping, 9-11 September 2014, Gothenburg, Sweden.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The control of NOx and SOx in chemical-looping combustion systems is discussed with the focus on the importance of the pressurized flue-gas train. The chemistry of nitrogen and sulfur under pressurized conditions and the experiences gained from operating oxy-fuel combustion pilot plants that pertain to chemical looping are reviewed. In the flue gases from the combustion process, SO2 and NO are the principle NOx and SOx species. The oxidation of NO to NO2 is favored by low temperature and high pressure and is enhanced during the compression of flue gases. The oxidation of NO to NO2 in the flue-gas train is significant at pressures >15 bar. The solubilities of NO2 and SO2 in water are high and results in the formation of acids. Once NOx and SOx are absorbed, the liquid-phase N-S interactions lead to the formation of sulfuric and nitric acids. Thus, the chemistry of NOx and SOx is of importance for flue-gas conditioning of chemical-looping combustion systems. Similar to oxy-fuel combustion, the conditions in the chemical-looping flue-gas train offer new opportunities for the design of NOx and SOx removal processes.
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| 24. |
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| 25. |
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| 26. |
- Ajdari, Sima, 1985, et al.
(författare)
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Reduced Mechanism for Nitrogen and Sulfur Chemistry in Pressurized Flue Gas Systems
- 2016
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 55:19, s. 5514-5525
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Tidskriftsartikel (refereegranskat)abstract
- The gas- and liquid-phase chemistry of nitrogen and sulfur species under pressurized conditions is of high importance to the design and performance of the pressurized flue gas systems in carbon capture and storage (CCS) schemes. Yet, the available description of this chemistry is complex and difficult to apply in design studies for removal of NOx and SOx during the compression. This work proposes a reduced mechanism for engineering calculations of pressurized flue gas systems, a mechanism that is able to describe the relevant gas and liquid-phase chemistry as well as the S/N-product distribution. The reduced mechanism is derived by identifying the rate-limiting reactions using sensitivity analysis. The performance of the mechanism subsets are compared with results of a detailed mechanism. The identified rate-limiting reactions for the formation of key products form the basis for two different types of reduced mechanisms. The sets include one general reduced mechanism (valid for all pH conditions) and sets of pH-specific mechanisms. The general reduced mechanism and the pH-specific mechanisms perform satisfactorily compared to the detailed mechanism under different pH conditions. The results show that depending on the purpose of the modeling, whether it is to predict the pollutant removal (where sulfurous acid and nitrogen acids are mainly important) or capture the liquid composition, for which the N-S chemistry products are also important, different levels of simplification can be made. The number of reactions is reduced from 34 reactions (39 species) in the detailed mechanism to 12 reactions (20 species) in the general reduced mechanism and 7-8 (14-17 species) in the pH-specific mechanisms.
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| 27. |
- Akbari, Saeed, et al.
(författare)
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Ceramic Additive Manufacturing Potential for Power Electronics Packaging
- 2022
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Ingår i: IEEE Transactions on Components, Packaging, and Manufacturing Technology. - : Institute of Electrical and Electronics Engineers Inc.. - 2156-3950 .- 2156-3985. ; 12:11, s. 1857-1866
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Tidskriftsartikel (refereegranskat)abstract
- Compared with silicon-based power devices, wide band gap (WBG) semiconductor devices operate at significantly higher power densities required in applications such as electric vehicles and more electric airplanes. This necessitates development of power electronics packages with enhanced thermal characteristics that fulfil the electrical insulation requirements. The present research investigates the feasibility of using ceramic additive manufacturing (AM), also known as three-dimensional (3D) printing, to address thermal and electrical requirements in packaging gallium nitride (GaN) based high-electron-mobility transistors (HEMTs). The goal is to exploit design freedom and manufacturing flexibility provided by ceramic AM to fabricate power device packages with a lower junction-to-ambient thermal resistance (RθJA). Ceramic AM also enables incorporation of intricate 3D features into the package structure in order to control the isolation distance between the package source and drain contact pads. Moreover, AM allows to fabricate different parts of the packaging assembly as a single structure to avoid high thermal resistance interfaces. For example, the ceramic package and the ceramic heatsink can be printed as a single part without any bonding layer. Thermal simulations under different thermal loading and cooling conditions show the improvement of thermal performance of the package fabricated by ceramic AM. If assisted by an efficient cooling strategy, the proposed package has the potential to reduce RθJA by up to 48%. The results of the preliminary efforts to fabricate the ceramic package by AM are presented, and the challenges that have to be overcome for further development of this manufacturing method are recognized and discussed.
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| 28. |
- Akbari, Saaed, et al.
(författare)
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Effect of PCB cracks on thermal cycling reliability of passive microelectronic components with single-grained solder joints
- 2019
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Ingår i: Microelectronics and reliability. - : Elsevier BV. - 0026-2714 .- 1872-941X. ; 93, s. 61-71
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free tin-based solder joints often have a single-grained structure with random orientation and highly anisotropic properties. These alloys are typically stiffer than lead-based solders, hence transfer more stress to printed circuit boards (PCBs) during thermal cycling. This may lead to cracking of the PCB laminate close to the solder joints, which could increase the PCB flexibility, alleviate strain on the solder joints, and thereby enhance the solder fatigue life. If this happens during accelerated thermal cycling it may result in overestimating the lifetime of solder joints in field conditions. In this study, the grain structure of SAC305 solder joints connecting ceramic resistors to PCBs was studied using polarized light microscopy and was found to be mostly single-grained. After thermal cycling, cracks were observed in the PCB under the solder joints. These cracks were likely formed at the early stages of thermal cycling prior to damage initiation in the solder. A finite element model incorporating temperature-dependant anisotropic thermal and mechanical properties of single-grained solder joints is developed to study these observations in detail. The model is able to predict the location of damage initiation in the PCB and the solder joints of ceramic resistors with reasonable accuracy. It also shows that the PCB cracks of even very small lengths may significantly reduce accumulated creep strain and creep work in the solder joints. The proposed model is also able to evaluate the influence of solder anisotropy on damage evolution in the neighbouring (opposite) solder joints of a ceramic resistor.
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| 29. |
- Akbari, Saeed, et al.
(författare)
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Low Inductive SiC Power Electronics Module with Flexible PCB Interconnections and 3D Printed Casing
- 2022
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Ingår i: 2022 IMAPS Nordic Conference on Microelectronics Packaging, NordPac 2022. - : Institute of Electrical and Electronics Engineers Inc.. - 9789189711396
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Konferensbidrag (refereegranskat)abstract
- Silicon carbide (SiC) power devices are steadily increasing their market share in various power electronics applications. However, they require low-inductive packaging in order to realize their full potential. In this research, low-inductive layouts for half-bridge power modules, using a direct bonded copper (DBC) substrate, that are suitable for SiC power devices, were designed and tested. To reduce the negative effects of the switching transients on the gate voltage, flexible printed circuit boards (PCBs) were used to interconnect the gate and source pins of the module with the corresponding pads of the power chips. In addition, conductive springs were used as low inductive, solder-free contacts for the module power terminals. The module casing and lid were produced using additive manufacturing, also known as 3D printing, to create a compact design. It is shown that the inductance of this module is significantly lower than the commercially available modules.
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| 30. |
- Akbari, Saeed, et al.
(författare)
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Packaging Induced Stresses in Embedded and Molded GaN Power Electronics Components
- 2023
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Ingår i: Int. Conf. Therm., Mech. Multi-Phys. Simul. Exp. Microelectron. Microsyst., EuroSimE. - : Institute of Electrical and Electronics Engineers Inc..
-
Konferensbidrag (refereegranskat)abstract
- Residual stresses created during the packaging process can adversely affect the reliability of electronics components. We used incremental hole-drilling method, following the ASTM E 837-20 standard, to measure packaging induced residual stresses in discrete packages of power electronics components. For this purpose, we bonded a strain gauge on the surface of a Gallium Nitride (GaN) power component, drilled a hole through the thickness of the component in several incremental steps, recorded the relaxed strain data on the sample surface using the strain gauge, and finally calculated the residual stresses from the measured strain data. The recorded strains and the residual stresses are related by the compliance coefficients. For the hole drilling method in the isotropic materials, the compliance coefficients are calculated from the analytical solutions, and available in the ASTM standard. But for the orthotropic multilayered components typically found in microelectronics assemblies, numerical solutions are necessary. We developed a subroutine in ANSYS APDL to calculate the compliance coefficients of the hole drilling test in the molded and embedded power electronics components. This can extend the capability of the hole drilling method to determine residual stresses in more complex layered structures found in electronics.
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| 31. |
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| 32. |
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| 33. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Alkali sulfation during combustion of coal in a pilot scale facility using additives to alter the global sulfur to potassium and chlorine to potassium ratios
- 2021
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:3, s. 4171-4178
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Tidskriftsartikel (refereegranskat)abstract
- Due to the urgent needs to reduce anthropogenic carbon dioxide emissions there is an increasing interest in the use of alternative fuels. For this reason, there is a need for new knowledge on how to design and adapt existing heat and power plants to biogenic and waste-derived fuels. This work relates to co-firing of biomass and coal and the sulfation of alkali chlorides in coal-fired flames doped with chemical additives. We aim to examine the global time scales of alkali sulfation and chlorination based on combustion experiments that were conducted in a 30-kW coal flame. Temperature, gas and particle composition measurements were conducted. Both experiments and modelling support that the apparent alkali sulfation kinetics are fast in a coal-fired flame and that it is dominated entirely by the presence of SO 2. The availability of oxygen and carbon monoxide, or hydrocarbons, is also critical to sustain the sulfation reaction cycle; low concentrations are sufficient. For industrial boilers this implies that sulfur addition, in combination with reburning, should constitute an efficient strategy to mitigate alkali-chlorination and the related high temperature corrosion.
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| 34. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Chemical Interactions between Potassium, Sulfur, Chlorine, and Carbon Monoxide in Air and Oxy-fuel Atmospheres
- 2020
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 34:1, s. 900-906
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents experimental and modeling work on the interaction between the K, Cl, and S components, and these chemical interactions are studied in both air-fuel and oxy-fuel atmospheres. Detailed kinetic modeling is conducted to examine the potassium chloride sulfation and its interaction with CO oxidation in both nitrogen- and carbon-dioxide-based atmospheres. The oxidation of CO enhances the kinetics of alkali sulfation for typical post-flame conditions, below 1000 °C, in both atmospheres. For higher temperatures, sulfation kinetics are promoted even further in CO2-rich atmospheres. Oxy-fuel atmospheres, i.e., CO2-rich atmospheres, also promote increased levels of CO in technical-scale flames. Therefore, in practical systems, enhanced sulfation kinetics will automatically be promoted by flue gas recirculation. Also, the availability of sulfur, in the form of an increased SO2 concentration, often enables complete sulfation of alkali in oxy-fuel atmospheres as a result of the flue gas recirculation. The availability of SO3 may increase in oxy-fuel compared to air-fuel atmospheres as a result of either elevated SO2 levels or different sulfation reaction patterns, as discussed in the modeling of this work. However, SO3 has no significant impact on the overall sulfation rates in oxy- compared to air-fired systems.
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| 35. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Influence of KCI and SO2 on NO Formation in C3H8 Flames
- 2017
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 31:10, s. 11413-11423
-
Tidskriftsartikel (refereegranskat)abstract
- The use of low-quality fuels in power generation plants is typically motivated by the potential for reducing fuel costs or CO2 emissions, the latter in the case of a fuel based on biomass. These features make low-quality fuels attractive, although their use for power generation is usually problematic due to their composition. One of the main issues is high-temperature corrosion (HTC), which is caused by alkali-containing chlorides. The alkali chlorides, which are formed from alkali metals and chlorine released from the fuel during the combustion process, are a particular problem. HTC is often related to the combustion of fuels with a low sulfur-to-potassium ratio, such as biomass, and it has a significant effect on the thermal efficiency and/or the maintenance cost of the power plant. Sulfuric and alkali species not only influence the formation of highly corrosive salts but also affect other aspects of combustion chemistry. While the present work relates to HTC chemistry, it focuses on how potassium chloride and sulfur dioxide influence the formation of NO. The experiments were carried out in a 100 kW test facility using C3H8 as the fuel. In order to examine the influence of SO2 and KCI on combustion, these two components were injected into the combustion reactor. In the experiments, pure gaseous SO2 was injected upstream of the burner. KCI was fed as an aqueous solution (3.34%, of KCI) that was sprayed directly into the flame. Pure water was also injected, to distinguish any possible interaction between KCI and water. Kinetic modeling was conducted to examine the reaction routes and activities. The results show that both KCI and SO2 suppress the formation of NO. KCI appears to inhibit the formation of NO, whereas SO2 decreases the concentration of NO by enhancing its oxidation to NO2.
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| 36. |
- Allgurén, Thomas, 1986, et al.
(författare)
-
NO formation during co-combustion of coal with two thermally treated biomasses
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The behavior of biomass as a fuel varies a lot. Not only between different sources of raw material, but also depending on if they have been pre-treated, and if so, also depending on the type of treatment. Two types of thermal pre-treatments of woody biomass used for combustion in suspension systems are torrefaction and steam explosion. These two types of pre-treated biomass were investigated in this work with focus on the nitrogen chemistry, and were investigated both experimentally in a 1.5MWth combustion unit and by performing detailed reaction simulations. Three different cases have been investigated. One case with 100% Utah Sufco coal and two cases where 15% of the coal (on a mass basis) has been replaced with either torrefied or steam exploded biomass. Even though only 15% of the coal has been substituted there is a clear difference in the amount of NO formed between the cases. The pure coal had the highest amount of NO formed which was expected due to the higher amount of fuel-bound nitrogen in the coal compared to the biomasses. The fuel analyses indicate that the nitrogen content is the same in the two investigated bio fuels. Despite this fact, the amount of NO formed was when coal was co-fired with torrefied biomass than with steam exploded biomass. The gas composition data from the in-flame measurements show that the concentration of volatile nitrogen species (HCN and NH3) varies between the cases, which is suggested as the reason for the difference in the NO formation. The importance of when and where the nitrogen species are released is also shown in the modelling work, supporting what was observed experimentally.
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| 37. |
- Allgurén, Thomas, 1986, et al.
(författare)
-
NO formation during co-combustion of coal with two thermally treated biomasses
- 2022
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 235
-
Tidskriftsartikel (refereegranskat)abstract
- The combustion behavior of biomass as a fuel varies dependent on source of the raw material, but also on the type of pre-treatment. In this work steam exploded and torrefied woody biomass were studied with respect to NOx formation in co-firing experiments. Most of the reported data is based on small scale experiments and simulations. In this work, however, have three different cases been investigated experimentally in a 1.5MW(th) combustor supported by reaction simulations. One case corresponds to firing 100% Utah bituminous coal and two cases where 15% of the coal (on a mass basis) has been replaced with either torrefied or steam exploded biomass. Two of the cases was also studied in a utility scale 1.3 GW(th) industrial boiler. In both units did the case with pure coal result in the highest amount of NO formed, which was expected due to the higher amount of fuel-bound nitrogen in the coal, as compared to the biomass fuels. The fuel analyses indicate that the nitrogen content is the same in the two investigated biofuels. However, the amount of NO formed differed. Gas composition measurements reveal that the partitioning of volatile nitrogen species (HCN and NH3) varies between the biomass co-firing cases. This was investigated further using detailed reaction simulations and is suggested as the main reason for the observed difference in NO formation.
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| 38. |
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| 39. |
- Allgurén, Thomas, 1986, et al.
(författare)
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The Influence of Alkali, Chlorine and Sulfur on Aerosol Formation
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of low-quality fuels in power generation is typically motivated by a potential reduction in fuel costs or CO2 emissions, the latter in case the fuel is based on biomass. These features make low quality fuels attractive at the same time as such fuels are usually problematic to use in power generation due to fuel composition. One of the main issues is deposition of aerosols upon heating surfaces reducing heat transfer and causing high-temperature corrosion (HTC). The later most often related to alkali chlorides, and these are formed from alkali species and chlorine when released during the combustion process. The present work aims to investigate how the gas phase chemistry are connected to the formation aerosols and their characteristics. This is an ongoing work why only part of the preliminary results is presented focusing on the interaction between alkali, sulfur and chlorine in the gas phase. The results presented here indicate a clear correlation between the S/Cl ratio and the formation of alkali sulfates over chlorides. It is also indicated that the local conditions at which the species are released and available in the gas phase is important for the resulting formation of alkali sulfates.
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| 40. |
- Andersson, Dag, et al.
(författare)
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COSIVU - Compact, smart and reliable drive unit for fully electric vehicles
- 2016
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Ingår i: 2016 Pan Pacific Microelectronics Symposium (Pan Pacific). - : Institute of Electrical and Electronics Engineers Inc.. - 9780988887398
-
Konferensbidrag (refereegranskat)abstract
- COSIVU is a three year collaborative research project that ended in September 2015 and which has been funded within the European Green Car Initiative (now the European Green Vehicle Initiative). COSIVU addresses one of the most critical technical parts in fully electrical vehicles (FEV) besides the energy storage system: the mechatronic drive-train unit. The COSIVU project has delivered a new system architecture for multiple wheel drive-trains by a smart, compact and durable single-wheel drive unit with integrated electric motor, full silicon carbide (SiC) power electronics (switches and diodes), a novel control and health monitoring module with wireless communication, and an advanced ultra-compact cooling solution. DfR utilizing FEM simulations ensures first time right solutions. This paper presents the main results including the architecture of the drive train solution as well as the modular design of the inverter based on Inverter Building Blocks, one per phase. Performance tests are presented here for the first time for both the heavy duty commercial vehicle solution performed in a test rig by Volvo, and the tests of the COSIVU solution adapted to a passenger car done by Elaphe.
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| 41. |
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| 42. |
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| 43. |
- Andersson, Joakim, et al.
(författare)
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Diamanter blir var mans egendom
- 2003
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Ingår i: Forskning & Framsteg. ; :1, s. 38-41
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 44. |
- Andersson, Klas, 1977, et al.
(författare)
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3D-Modelling of the Radiative Heat Transfer in Rotary Kilns with a Present Bed Material
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work presents a 3D-model of the radiative heat transfer in cylindrical furnaces with a present bed material. Experimental data gathered in a down-scaled version of a rotary kiln has been used as input data to the model analysis. In future work, the model is to be used to study full-scale rotary kilns used in different industries such as the iron ore industry, heating and sintering iron ore pellets.
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| 45. |
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| 46. |
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| 47. |
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| 48. |
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| 49. |
- Andersson, Klas, 1977
(författare)
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Characterization of oxy-fuel flames - their composition, temperature and radiation
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Oxy-fuel combustion is receiving growing attention as one of the promising CO2 capture technologies in connection to power production. Yet, significant efforts are required in research and development of this combustion process in order to be able to design and optimize a full scale power plant. In oxy-fuel combustion, the fuel is burnt with oxygen of high purity instead of air. Typically, a large amount of flue gas is recycled back to the combustion chamber to adjust the flame temperature and heat transfer conditions. As a consequence, the system is in principle free from air borne N2, whereas the combustion products, such as CO2, H2O, NOx and SOx, are accumulated to different degree in the system, which has implications on both combustion and heat transfer related processes. This work focuses on the flame and radiation characteristics and the emissions formed during oxy-fuel combustion of both gas and coal. The work is based on experiments carried out in a 100 kW oxy-fuel test facility, which was designed and constructed as a part of this work. In the present work dry recycling conditions were applied to study the effect of CO2 on the properties mentioned.The experiments show that the temperature, radiation, composition and ignition of the oxy-fuel flames are effectively controlled by the flue gas recycle rate. The gas and particle radiation was studied during combustion of both propane and lignite. The total radiation intensity was measured and compared against model results of the gas radiation intensity. In the propane oxy-fuel flame it is seen that the spectrally continuous radiation from soot is significantly influenced by the amount of CO2 recycled. Thus, in addition to effects on flame temperature and gas band radiation, the amount of CO2 recycled may have an important impact on the particle radiation. The same methodology was applied to study these relationships also in the lignite flames. The share of gas radiation in high temperature regions of the flame increases from about 30% during air-firing up to 45% in the oxy-fuel flames. However, the particle radiation seems to be little influenced under oxy-fuel conditions. Thus, during oxy-fuel combustion of lignite and with the recycling conditions applied (i.e. with an O2 fraction between 25 and 29 vol.% in the RFG) the particle radiation still dominates the measured total radiation intensity signal in important parts of the flame, which reduces the influence of an increased gas radiation in the lignite-fired flames.The NO formation was measured and modeled during combustion of lignite. The experimental results show that the NO emission [mgMJ-1] is reduced to 25-30% of the emission typical for air-firing. The modeling gives that the lower emission from oxy-fuel combustion is explained a by faster rate of reduction of formed and recycled NO in the system. Furthermore, the complete gas phase nitrogen chemistry was modeled to evaluate the potential for primary NOx reduction measures by means of gas phase reduction paths. The results demonstrate two different strategies possible (which could be combined): reduction via reburning at low temperatures (around 1000ºC) or reverse Zeldovich at high temperatures (above 1500ºC). Besides being sensitive to temperature, reburning is closely related to the stoichiometric conditions whereas the reverse Zeldovich path requires absence (or near) of free N2 and a relatively long residence time in order to be effective.
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| 50. |
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