| 1. |
- Abramowski, A., et al.
(författare)
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Search for a Dark Matter Annihilation Signal from the Galactic Center Halo with HESS
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:16, s. 161301-
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Tidskriftsartikel (refereegranskat)abstract
- A search for a very-high-energy (VHE; >= 100 GeV) gamma-ray signal from self-annihilating particle dark matter (DM) is performed towards a region of projected distance r similar to 45-150 pc from the Galactic center. The background-subtracted gamma-ray spectrum measured with the High Energy Stereoscopic System (H.E.S.S.) gamma-ray instrument in the energy range between 300 GeV and 30 TeV shows no hint of a residual gamma-ray flux. Assuming conventional Navarro-Frenk-White and Einasto density profiles, limits are derived on the velocity-weighted annihilation cross section as a function of the DM particle mass. These are among the best reported so far for this energy range and in particular differ only little between the chosen density profile parametrizations. In particular, for the DM particle mass of similar to 1 TeV, values for above 3 x 10(-25) cm(3) s(-1) are excluded for the Einasto density profile.
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| 2. |
- Boman, Christoffer, et al.
(författare)
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Development of innovative small(micro)-scale biomass-based CHP technologies
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- To enhance the overall efficiency of the use of biomass in the energy sector in Europe, the large electricity production potential from small-scale biomass heating systems should be utilised. So far, no technologically sound (in terms of efficiency and reliability) and economically affordable micro- and small-scale biomass CHP technologies are, however, available. Therefore, the present ERA-NET project (MiniBioCHP) aimed at the further development and test of new CHP technologies based on small-scale biomass combustion in the electric capacity range between some W and 100 kW. Within the project, an international consortium consisting of 12 partners from 4 countries, including university institutions, institutes and industry (both engineering and manufacturing), collaborated closely to perform high level R&D on three promising micro/small-scale biomass based CHP technologies which are covering a broad range of applications in the residential heating sector. The Austrian engineering company BIOS, coordinated the international project. The project was based on earlier basic research and development work related to these promising new technologies and aimed at the achievement of a technological level which allows a first (commercial) demonstration after the end of the project. The three CHP concepts included in the MiniBioCHP project were;1. Pellet stoves with a thermoelectric generator (TEG)2. Small-scale biomass boilers (10-30 kWth) with a micro-ORC process3. High temperature heat exchanger (HT-HE) for an externally fired gas turbine (EFGT)The Swedish part of the project was focused on the development of the concept of biomass based EFGT with dedicated R&D activities related to the development of the HT-HE system. The Swedish project consisted of the research partners Umeå University (project leader), Luleå University of Technology, Chalmers University of Technology and RISE Research Institutes of Sweden, together with the industrial partners Enertech AB/Osby Parca and Ecergy. The expertise of the Swedish partners regarding ash related problems, grate boiler combustion and modelling, deposit formation and high temperature corrosion, were combined with the know-how of a Polish partner regarding HT-HE design, construction, testing and optimisation.The HT-HE is the most crucial component in EFGT processes significantly influencing the investment costs, availabilities as well as the efficiencies that can be achieved. With a thermal capacity from several hundred kW up to 2-3 MWth) the CHP technology based on a biomass boiler and an EFGT is suitable for district heating systems, or process heat consumers. The electricity produced by the gas turbine (up to some 100 kWel) can be used to cover the own electricity consumption of a company and/or fed into the grid. Even though the concept of biomass based EFGT has been an interesting alternative for small-scale CHP production for some decades, and R&D activities have been undertaken, tackling both economic and technical aspects, only a few pilot-plants have been in operation and no initiative has so far reached the level of commercial implementation. Thus, the concept of EFGT fed with biomass is still considered to be in a rather early development stage and the main technical challenges are related to alkali deposit induced corrosion and thermal stress of the HT-HE material, turbine design/operation and system integration.Within the present project, a HT-HE prototype aimed for an EFGT system was therefore designed, constructed and successfully tested at flue gas temperatures up to 900°C. Thus, appropriate guidelines for a compact design of the HT-HE and recommendations have been worked out to minimize thermal stresses as well as ash related problems regarding ash deposit formation and high temperature corrosion in a biomass boiler system. Furthermore, different concepts for the overall biomass based EFGT system have been worked out and evaluated. The outcome of the project will hopefully be used in the further development work and form the basis for a first testing and demonstration plant within the coming years.
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| 3. |
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| 4. |
- Niklasson, Fredrik, et al.
(författare)
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Branschgemensam forskning för småskaliga biobränslepannor inför ekodesign
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Nytillverkade småskaliga biobränslepannor måste uppfylla ekodesignkraven senast år 2020. I en marknadsundersökning från 2014 klarade ingen av 11 testade pelletspannor alla ställda krav, vilket tydligt visar på ett utvecklingsbehov. Föreliggande projekt har haft som syfte att panntillverkare och forskningsinstitut branschgemensamt ska bemöta de förbränningstekniska utmaningar som tillverkarna står inför.För pelletspannor är den största utmaningen med ekodesigndirektivet att prestanda till största delen beräknas från drift vid partiell last (låg last). Tidigare har prestanda bara fastställts vid nominell last och designen optimerats därefter. I detta projekt har tester körts med två moderna pelletspannor som har olika typer av pelletsbrännare: en med horisontellt brännarrör och en med undermatad brännarkopp. Resultaten visar att tillräckligt god förbränning kunde upprätthållas vid partiell last med båda brännartyperna. Dock uppvisade rörbrännaren betydligt lägre emissioner vid partiell last, troligtvis beroende på att förbränningszonen i denna brännare är skyddad från värmestrålningsutbyte med kylande pannväggar. Ett ganska omfattande arbete lades ned på att förse koppbrännaren med en skyddande krage som skulle skydda förbränningszonen. Det resulterade dock inte in någon betydande förbättring, antagligen beroende på att tillförseln av sekundärluft inte blev optimal. Ett mer omfattande arbete krävs för att utveckla en optimal brännardesign av denna typ.För vedpannor är det en utmaning att klara ekodesigndirektivets NOx-krav på 200 mg/Nm³. En mängd temperaturmätningar i en vedpanna för villabruk resulterade i att termisk NOx-bildning kunde uteslutas. Pannan förseddes med ett system för rökgasåterföring, men det minskade inte NOx-emissionen. Därefter provades olika vedsorter. NOx-emissionen kunde minskas till att klara gränsvärdet med avbarkad björkved. Kemiska analyser visade att björkbarken innehöll 0,49% kväve jämfört med 0,09% i stamveden. Även granved gav låga NOx-emissioner, men det bränslet medförde ökade emissioner av CO och OGC. För att vedpannor ska klara kraven på CO, OGC och stoft krävs optimering med avseende på vedens slutförbränningsfas. I det skedet är emissionerna som högst, vilket beror på att värmeeffekten avtar och luftflödet tenderar att kyla ned rökgasen innan de brännbara gaserna brunnit ut. Den optiska partikelmätningen visade tydlig korrelation mellan stoft och CO i rökgasen. Om pannan uppfyller gränsvärdet för CO så finns goda chanser att även kravet på partiklar uppfylls.Verkningsgraden som anges i ekodesigndirektivet beräknas utgående från bränslets övre värmevärde. Dessutom subtraheras vissa förlustfaktorer. Detta innebär att pannan inte får ha några onödigt stora värmeförluster eller omotiverat hög elförbrukning för att klara satta krav. Mätningar visade att den största förlusten sker via värmen i rökgasen. Den näst största förlustposten är värmetransport från pannkroppen. För verkningsgraden ökar betydelsen av en välisolerad pannkropp vid partiell last. De två pelletspannor som användes inom projektet låg väl till för att kunna uppfylla ekodesigndirektivets krav på verkningsgrad.
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| 5. |
- Niklasson, Fredrik, 1968-, et al.
(författare)
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On-line monitoring of agglomeration in fluidised bed boilers
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Combustion in fluidized beds has several benefits, but a potential problem is bed agglomeration causing defluidisation. The most used counter measure is to regularly renew the bed material, inferring costs for new sand and deposition of spent material. For an adaptive optimization there is a need of a method which indicates when bed agglomeration is initializing, before it is too late to counteract.In this project, the conductivity of fluidized beds has been measured by a novel in-situ probe. The probe has been tested in a fluidized bed of sand and ashes at temperatures up to 1000°C. In addition, the probe has been tested in a fluidized bed while burning different fuels.The results show that the conductivity of the bed increases with temperature and concentration of ash. The conductivity varies strongly between different fuels. The signal from the probe reacts strongly to the onset of severe bed agglomeration, but it is hard to find any consistent tendencies that can be applied to predict it.
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| 6. |
- Verteramo, Maria Luisa, et al.
(författare)
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Interplay of halogen bonding and solvation in protein-ligand binding
- 2024
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Ingår i: iScience. - 2589-0042. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- Halogen bonding is increasingly utilized in efforts to achieve high affinity and selectivity of molecules designed to bind proteins, making it paramount to understand the relationship between structure, dynamics, and thermodynamic driving forces. We present a detailed analysis addressing this problem using a series of protein-ligand complexes involving single halogen substitutions - F, Cl, Br, and I - and nearly identical structures. Isothermal titration calorimetry reveals an increasingly favorable binding enthalpy from F to I that correlates with the halogen size and σ-hole electropositive character, but is partially counteracted by unfavorable entropy, which is constant from F to Cl and Br, but worse for I. Consequently, the binding free energy is roughly equal for Cl, Br, and I. QM and solvation-free-energy calculations reflect an intricate balance between halogen bonding, hydrogen bonds, and solvation. These advances have the potential to aid future drug design initiatives involving halogenated compounds.
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