| 1. |
- Abazajian, Kevork, et al.
(författare)
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CMB-S4 : Forecasting Constraints on Primordial Gravitational Waves
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 926:1
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Tidskriftsartikel (refereegranskat)abstract
- CMB-S4—the next-generation ground-based cosmic microwave background (CMB) experiment—is set to significantly advance the sensitivity of CMB measurements and enhance our understanding of the origin and evolution of the universe. Among the science cases pursued with CMB-S4, the quest for detecting primordial gravitational waves is a central driver of the experimental design. This work details the development of a forecasting framework that includes a power-spectrum-based semianalytic projection tool, targeted explicitly toward optimizing constraints on the tensor-to-scalar ratio, r, in the presence of Galactic foregrounds and gravitational lensing of the CMB. This framework is unique in its direct use of information from the achieved performance of current Stage 2–3 CMB experiments to robustly forecast the science reach of upcoming CMB-polarization endeavors. The methodology allows for rapid iteration over experimental configurations and offers a flexible way to optimize the design of future experiments, given a desired scientific goal. To form a closed-loop process, we couple this semianalytic tool with map-based validation studies, which allow for the injection of additional complexity and verification of our forecasts with several independent analysis methods. We document multiple rounds of forecasts for CMB-S4 using this process and the resulting establishment of the current reference design of the primordial gravitational-wave component of the Stage-4 experiment, optimized to achieve our science goals of detecting primordial gravitational waves for r > 0.003 at greater than 5σ, or in the absence of a detection, of reaching an upper limit of r < 0.001 at 95% CL.
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| 2. |
- Albert, A., et al.
(författare)
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SEARCHING FOR DARK MATTER ANNIHILATION IN RECENTLY DISCOVERED MILKY WAY SATELLITES WITH FERMI-LAT
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 834:2
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Tidskriftsartikel (refereegranskat)abstract
- We search for excess gamma-ray emission coincident with the positions of confirmed and candidate Milky Way satellite galaxies using six years of data from the Fermi Large Area Telescope (LAT). Our sample of 45 stellar systems includes 28 kinematically confirmed dark-matter-dominated dwarf spheroidal galaxies (dSphs) and 17 recently discovered systems that have photometric characteristics consistent with the population of known dSphs. For each of these targets, the relative predicted gamma-ray flux due to dark matter annihilation is taken from kinematic analysis if available, and estimated from a distance-based scaling relation otherwise, assuming that the stellar systems are DM-dominated dSphs. LAT data coincident with four of the newly discovered targets show a slight preference (each similar to 2 sigma local) for gamma-ray emission in excess of the background. However, the ensemble of derived gamma-ray flux upper limits for individual targets is consistent with the expectation from analyzing random blank-sky regions, and a combined analysis of the population of stellar systems yields no globally significant excess (global significance < 1 sigma). Our analysis has increased sensitivity compared to the analysis of 15 confirmed dSphs by Ackermann et al. The observed constraints on the DM annihilation cross section are statistically consistent with the background expectation, improving by a factor of similar to 2 for large DM masses (m(DM, b<(b)over bar>) greater than or similar to 1 TeV and m(DM, tau+tau-) greater than or similar to 70 GeV) and weakening by a factor of similar to 1.5 at lower masses relative to previously observed limits.
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| 3. |
- Andersson, Kent, 1967-, et al.
(författare)
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Introduktion till Operationsanalys : En antologi med essäer av studerande i militärteknik 2011
- 2012
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- I ämnesplanen definieras militärteknik som ”den vetenskap som beskriver och förklarar hur tekniken inverkar på militär verksamhet på alla nivåer, strategisk, operativ och taktisk, samt hur officersprofessionen påverkar och påverkas av tekniken.”[1] En militärteknikers uppgift brukar, utgående från definitionen, uttryckas som att beskriva och förklara den militära nyttan med tekniken. För att kunna göra detta behövs verktyg. Och många av dem kommer från den vetenskapliga disciplinen Operationsanalys.Syftet med den här antologin är att introducera studerande i militärteknik på Försvarshögskolan till två av de mest refererade boktitlarna i operationsanalys – Methods for conducting military operational analysis editerad av Andrew G. Loerch och Larry B. Rainey samt Military Operations Research, quantitative decision making av N.K. Jaiswal.Kapitlen utgörs av essäer skrivna av studerande på den högre stabsofficersutbildningen med teknisk inriktning, som examinationsuppgift i en fördjupningskurs. Essäerna är till del referat av kapitel i de två böckerna ovan, men kryddade med exempel satta i svenskt sammanhang och med de studerandes egen värdering av metodernas användbarhet.[1]Försvarshögskolan, Ämnesplan militärteknik, 2007.
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| 4. |
- Drlica-Wagner, A., et al.
(författare)
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SEARCH FOR GAMMA-RAY EMISSION FROM DES DWARF SPHEROIDAL GALAXY CANDIDATES WITH FERMI-LAT DATA
- 2015
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 809:1
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Tidskriftsartikel (refereegranskat)abstract
- Due to their proximity, high dark-matter (DM) content, and apparent absence of non-thermal processes, Milky Way dwarf spheroidal satellite galaxies (dSphs) are excellent targets for the indirect detection of DM. Recently, eight new dSph candidates were discovered using the first year of data from the Dark Energy Survey (DES). We searched for gamma-ray emission coincident with the positions of these new objects in six years of Fermi Large Area Telescope data. We found no significant excesses of gamma-ray emission. Under the assumption that the DES candidates are dSphs with DM halo properties similar to the known dSphs, we computed individual and combined limits on the velocity-averaged DM annihilation cross section for these new targets. If the estimated DM content of these dSph candidates is confirmed, they will constrain the annihilation cross section to lie below the thermal relic cross section for DM particles with masses less than or similar to 20 GeV annihilating via the b (b) over bar or pi(+)pi(-) channels.
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| 5. |
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| 6. |
- Haupt, Dan, et al.
(författare)
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Aftertreatment strategy for reducing emissions from an ethanol fueled CI engine
- 2009
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Ingår i: SAE 2009 International Powertrains, Fuels & Lubricants Meeting. - Warrendale, Pa. : Society of Automotive Engineers, Incorporated.
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Konferensbidrag (refereegranskat)abstract
- A nine liters ethanol-fueled CI engine was equipped with aftertreatment devices while different ratios of exhaust gas recirculation (EGR) were tested. The NO\dX emissions were negatively correlated to the EGR-ratio and NO\dX reductions of between 33% and 73% were obtained. Unfortunately, the decrease in NO\dX was followed by increased emissions of carbon monoxide, hydrocarbons, particulate matter and higher fuel consumption. The particle number emission increased approximately 4 times and particle sizes above 200 nm became more frequent when using EGR. The remedy for these emissions was to combine an oxidation catalyst and a diesel particle filter (DPF), while keeping the EGR-ratio low to minimize fuel consumption. Equipped like this, the engine passed the Euro 5 regulation as well as the Enhanced Environmentally Friendly Vehicles standard (EEV).
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| 7. |
- Haupt, Dan, et al.
(författare)
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Emissioner och emissionsfaktorer från fyra arbetsmaskiner : mätning av reglerade och ickereglerade emissioner
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Arbetsmaskiner förbrukar en mycket stor del av det dieselbränsle som används i landet. En stor del av avgasemissionerna härrör följaktligen från dessa maskiner. Det är därför viktigt att ta fram kunskap om vilka emissioner som avges och på vilka olika sätt emissionerna kan minskas. Som ett led i detta arbete har projektet "Utveckling av relevanta arbetscykler och emissionsfaktorer samt reducering av bränsleförbrukningen för arbetsmaskiner" (EMMA) genomförts. Projektet har finansierats av Kommunikationsforskningsberedningen (numera en del av VINNOVA), Energimyndigheten, Vägverket och LRF. Dessutom har Volvo Wheel Loaders ställt motorer och Valtra Traktor AB traktorer och motorer tillprojektets förfogande. Vidare har JTI disponerat en större traktor från Lantmännens Maskin Import AB.Projektet har genomförts av ett konsortium bestående av:Luleå tekniska universitet (LTU)JTI - Institutet för jordbruks- och miljöteknik (JTI)Institutionen för lantbruksteknik SLU (LT)SkogForsk (Skog)Svensk Maskinprovning AB (SMP)Vägverket Produktion (VägvP)I denna rapport sammanfattar Luleå Tekniska Universitet sina resultat från emissionsmätningarna i EMMA projektet. Mätningarna omfattar fyra arbetsmaskiner som har körts i motorprovbänk enligt en 22- punkters testcykel. Motorerna som testades var en Sisu Diesel 620 DWRE, en Volvo TD63 KDE, en Volvo TD40 GJE samt en Sisu diesel 420 DWRE. Motorerna testades vid Luleå Tekniska Universitets motorlaboratorium samt vid Svensk maskinprovning i Umeå. Både reglerade och icke-reglerade emissioner har uppmätts. De reglerade emissionerna som har mätts är HC, NOX och CO. De icke reglerade komponenterna som analyserats är formaldehyd, acetaldehyd, akrolein, bensaldehyd, etan, eten, propan, propen, propyn, isobutan, acetylen, 1-buten, isobuten, pentan, 1,3-butadien, bensen, toluen, M-xylen och O-xylen.Genom att använda uppmätta tidsprocentvärden från ett antal olika arbetsoperationer, som därefter har fördelats enligt moderna i ISO 8178, har emissionsfaktorer för ett antal olika arbetsoperationer genererats.
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| 8. |
- Haupt, Dan, et al.
(författare)
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Hydrocarbons and aldehydes from a diesel engine running on ethanol and equipped with EGR, catalyst and DPF
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A commercially available exhaust aftertreatment system, DNO\dx\sT, comprising exhaust gas recirculation (EGR), an oxidative catalyst and a continuously regenerating diesel particulate filter (DPF) were tested. The test object was a 9-liter, ethanol-fueled diesel engine from Scania equipped with turbocharger and aftercooler. A similar diesel engine from Scania, but running on ordinary Swedish diesel fuel, was used as a reference and a reminder of "the state of the art." The tests involved two different ethanol fuels containing various ignition improvers, Beraid 3540 and rapeseed methyl ester. Test conditions for the engines were those specified in the European Stationary Cycle (ESC). The aftertreatment system reduced the emissions of HC, CO and NO\dx, down to 0.15, 0.04 and 2.54 g/kWh, respectively, while the estimated particle mass was reduced by 67%. Actually, by using the DNO\dx\sT system, the engines became Euro IV engines regarding the emissions of HC, CO and NO\dx. The ethanol-fueled engine without EGR, catalyst or DPF emitted approximately 1.6 times more formaldehyde and 9.8 times more acetaldehyde than the diesel engine. However, the emission of acrolein was only 0.47 times the emission of acrolein from the diesel engine. When the ethanol-fueled engine was equipped with DNO\dx\sT, a significant reduction of the emissions of aldehydes was obtained. The emissions of acrolein, formaldehyde and acetaldehyde were reduced by 56%, 87% and 95%, respectively. An even higher reduction was observed when the system was connected to the diesel engine. Fifteen different hydrocarbons (alkanes, olefins and monoaromates) were also identified. The diesel-fueled engine, without any exhaust aftertreatment devices, emitted approximately twice as much hydrocarbon than the ethanol-fueled engine, also without any exhaust aftertreatment devices. However, there were also qualitative differences. Three hydrocarbons, namely propene, ethene and benzene, accounted for 77% of the hydrocarbons emitted from the diesel-fueled engine, while acetylene, ethene and benzene, made up only 53% of the hydrocarbons emitted from the ethanol-fueled engine. When connecting the system to the engines, a difference was observed; the reduction of analyzed hydrocarbon emissions was approximately 90% for the diesel-fueled engine, but only 47% for the ethanol-fueled engine. The studied aftertreatment system has been developed and optimized for the diesel-fueled engine. This fact is reflected in the powerful reduction of hydrocarbons, aldehydes, particles and NO\dx that is obtained when connecting the system to the diesel-fueled engine. Nevertheless, a significant reduction is also obtained when connecting the system to the ethanol-fueled engine. Test results indicate that it should be possible to better optimize the system for the ethanol engine. It is also, probably, necessary to exchange the catalyst in the system. Thereby, an even higher reduction of unregulated and regulated emissions should be obtained
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| 9. |
- Haupt, Dan, et al.
(författare)
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Investigating the potential to obtain low emissions from a diesel engine running on ethanol and equipped with EGR, catalyst and DPF
- 2004
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Experiments were performed to investigate the potential to achieve low emissions from a diesel engine fueled by ethanol and equipped with a commercially available exhaust after-treatment device, DNO\dx\sT from STT Emtec. The DNO\dx\sT system includes exhaust gas recirculation (EGR) catalysts and a continuously regenerating diesel particulate filter (DPF). Two Euro III classified 9-liter turbocharged, after-cooled diesel engines from Scania were used for the task. One engine was fueled by ethanol and the other by Swedish diesel fuel, EC1. Engine operating conditions of a 22-mode test cycle, including the 13 modes of the European Stationary Cycle (ESC cycle), were used for the tests. The emissions of NO\dx and HC were small for the ethanol-fueled engine, 3.48 and 0.53 g/kWh, respectively, while the emission of CO was higher, 2.07 g/kWh. Estimations of emitted particle mass were calculated by using the software supplied in the Scanning Mobility Particle Sizer (SMPS). The estimations showed that the ethanol engine emitted only \mA1/10 of the particle mass emitted by the diesel-fueled engine. A powerful reduction of the regulated emissions was obtained when equipping the ethanol engine with EGR, catalyst and DPF. The emissions of HC, CO and NO\dx decreased down to 0.15, 0.04 and 2.54 g/kWh, respectively, while the estimated particle mass was reduced by 67%. Actually, by using the aftertreatment system, the engine became a Euro IV engine regarding the emissions of HC, CO and NO\dx. The system worked even better with the diesel-fueled engine. The NO\dx emission was reduced by approximately 33% and the estimated particle mass by more than 99%. Calculations showed that the EGR ratio was higher for the diesel engine than for the ethanol engine. Consequently, by applying a higher EGR ratio for the ethanol engine an additional reduction of the NO\dx emissions should be obtained. The results indicate that very low NO\dx and particle emissions could be obtained for an ethanol-fueled diesel engine by using the right aftertreatment equipment. Future studies should investigate the possibility to increase the EGR ratio further. The investigations also underline the need for development of a special particulate filter for ethanol engines.
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| 10. |
- Nord, Kent E., et al.
(författare)
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Reducing the emission of particles from a diesel engine by adding an oxygenate to the fuel
- 2005
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 39:16, s. 6260-6265
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Tidskriftsartikel (refereegranskat)abstract
- Particulate and high emissions of NOx are the main problems that are associated with diesel engines. Therefore, techniques and fuels that promote a reduction in these emissions currently are attracting great interest In this paper, a mixture of acetal and regular diesel fuel has been tested in a heavy-duty diesel engine. The effect was a marked decrease in particle number and the estimated particle mass. A small reduction of the engine power was also observed; however, the net effect was nevertheless a reduction in the emission of CO₂ per European stationary cycle. The emissions of HC, CO, NOx ,some aldehydes, and hydrocarbons were only slightly affected by the new fuel composition. An exception was the emission of acetaldehyde, which was almost quadrupled, probably reflecting the decomposition and oxidation of acetal to acetaldehyde.
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