| 1. |
- Carlsson, Ella, et al.
(författare)
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Mass composition of the escaping plasma at Mars
- 2006
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Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 182:2, s. 320-328
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Tidskriftsartikel (refereegranskat)abstract
- Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO2+/O+ and O-2(+)/O+. The following ratios averaged over all events and energies were identified: CO2+/O+ = 0.2 and O-2(+)/O+ = 0.9. The values measured are significantly higher, by a factor of 10 for O-2(+)/O+, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O+, followed by O-2(+) and CO2+. We estimate the loss of CO2+ to be 4.0 x 10(24) s(-1) (0.29 kg s(-1)) by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.
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| 2. |
- Nilsson, Hans, et al.
(författare)
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Evolution of the ion environment of comet 67P/Churyumov-Gerasimenko
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 583
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Tidskriftsartikel (refereegranskat)abstract
- Context. The Rosetta spacecraft is escorting comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 AU, where the comet activity was low, until perihelion at 1.24 AU. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation. Aims. Using the Rosetta Plasma Consortium Ion Composition Analyzer (RPC-ICA), we study the gradual evolution of the comet ion environment, from the first detectable traces of water ions to the stage where cometary water ions accelerated to about 1 keV energy are abundant. We compare ion fluxes of solar wind and cometary origin. Methods. RPC-ICA is an ion mass spectrometer measuring ions of solar wind and cometary origins in the 10 eV-40 keV energy range. Results. We show how the flux of accelerated water ions with energies above 120 eV increases between 3.6 and 2.0 AU. The 24 h average increases by 4 orders of magnitude, mainly because high-flux periods become more common. The water ion energy spectra also become broader with time. This may indicate a larger and more uniform source region. At 2.0 AU the accelerated water ion flux is frequently of the same order as the solar wind proton flux. Water ions of 120 eV-few keV energy may thus constitute a significant part of the ions sputtering the nucleus surface. The ion density and mass in the comet vicinity is dominated by ions of cometary origin. The solar wind is deflected and the energy spectra broadened compared to an undisturbed solar wind. Conclusions. The flux of accelerated water ions moving from the upstream direction back toward the nucleus is a strongly nonlinear function of the heliocentric distance.
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| 3. |
- Carlson, Johan E., 1973-, et al.
(författare)
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Ulraljudsmetod för mätning av belastning på bergbultar : [Ultrasound Method for Measurement of Load on Rock Bolts]
- 2022
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Konferensbidrag (refereegranskat)abstract
- Inom både gruvindustri och infrastrukturprojekt är tillståndskontroll av bergbultar av stort intresse. Det finns dedikerade mätbultar som kan installeras för att detektera och följa förändringar över tid. Det finns även metoder för att kontrollera ingjutningen av bultar vid installation. Däremot saknas idag mätmetoder för att följa tillståndet hos generiska bergbultar över tid, eller för att detektera avvikelser bland sedan tidigare installerade bultar.I detta projekt utvecklas en metod baserad på ultraljud för att följa förändringar i mekaniska egenskaper över tid och för att kunna detektera avvikande bultar i en population av redan installerade bultar. Metoden bygger på en kort ultraljudspuls skickas in i bulten från den fria änden och att en reflekterat ljud från hela bultens längd samlas in. Detta fingeravtryck av bulten kan sedan jämföras bultar emellan, eller följas för en enskild bult över tid.För att demonstrera principen visar vi hur uppmätta ultraljudssignaturer kan användas för att modellera hela dragprovskurvan (kraft mot töjning), från vila till brottgräns för en c:a 3 meter lång dynamisk bergbult.
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| 4. |
- Carlsson, Ella, et al.
(författare)
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Analysis of the mass composition of the escaping plasma at Mars
- 2006
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Ingår i: 2006 European Geosciences Union General Assembly (EGU 2006), Austria Center Vienna, Vienna (Austria), 2-7 Apr 2006. - : European Geosciences Union (EGU).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Results from Mars Express, Mars Exploration Rovers and Mars Global Surveyor indicate that Mars harbored large amounts of liquid water on the surface in the past. In order for the water-associated geomorphologic features to form, the pressure in the atmosphere must have been at least a hundred times higher to produce the necessary greenhouse effect required to hold liquid water stable. The present atmospheric pressure is only 6-9 mbar and moreover, the spectral imaging of Mars suggests that the amount of carbonates stored in the surface is too low in order to explain the denser atmosphere in the past. This controversy led us to investigate the escaping plasma by analyzing the data from the IMA sensor (Ion Mass Analyzer) of the ASPERA-3 instrument suite onboard Mars Express. The IMA sensor measures the differential flow of ion components in the energy range of 0.01-30 keV/q.Since the instrument design was optimized for studies of plasma dynamics, the mass resolution is not adequate enough to directly resolve CO+2 from O+2 , which is the main molecular ion composing the Mars ionosphere according to theoretical models. Therefore, a special multi-species fitting technique, using calibration and in-flight data, was developed to resolve the CO+2 peak from the neighboring and much more intense O+2 peak. This technique was applied to the observations covering the period from April 4, 2004 to October 2, 2005. The events of heavy ion escape were identified inside the induced magnetosphere boundary and the Martian eclipse. We report the results of statistical studies of these ion-beam events which permitted to determine CO+2 / O+ and the O+2 / O+ ratio of the escaping plasma at Mars.
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| 5. |
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| 6. |
- Dalenbäck, J-O, et al.
(författare)
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Solar heated residential area Anneberg
- 2000
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Ingår i: Proceedings Third ISES Europe Solar Congress. - : International Solar Energy Society.
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Konferensbidrag (refereegranskat)abstract
- A solar heated area comprising 50 residential units is under construction. The system includes low-temperature space heating with seasonal ground storage of solar heat. Heating is supplied by 2 400 m{sup 2} of solar collectors and individual electrical heaters for supplementary heating. During the summer part of collected heat is stored in a borehole store with 100 boreholes drilled to 65 m depth. The groundwater-filled boreholes are fitted with double U-tubes. The average temperature of the seasonal store, about 60,000 m{sup 3} of crystalline rock, varies between 30 and 45 deg. C over the year. A floor heating system designed for a supply temperature of 32 deg. C provides space heating. The system is also equipped with buffer tanks for pre-heating of domestic hot water. The collectors will have favourable working conditions but the store is rather small and the estimated heat loss from the heat store is about 40% of collected solar heat. The average solar fraction is estimated to 70% and the resulting total heating cost is estimated to about 1 000 SEK/MWh ({approx}120{open_square}/MWh).
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| 7. |
- Lundin, Anders, et al.
(författare)
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Compressibility of C61D2 up to 1 GPa in the temperature range 175 - 345 K
- 1996
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Ingår i: Carbon. - : Elsevier Science Ltd.. - 0008-6223 .- 1873-3891. ; 34:9, s. 1119-1121
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the bulk modulus K for C61D2 up to 1 GPa in the temperature range 175–343 K. For face-centered cubic C61D2 above 290 K, we find an anomalously low value for K below about 0.15 GPa, possibly indicating pressure-induced changes in the structure. The (extrapolated) zero-p bulk modulus K(0) decreases with increasing T from 6.7 GPa at 175 K to 5.2 GPa at 343 K. A comparison with hypothetical expanded f.c.c. C60 with the same lattice constant shows that K(0) values are similar, indicating that the main intermolecular interactions are still between molecular bellies, not the sidegroups.
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| 8. |
- Lundin, Lars-Christer, et al.
(författare)
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Continuous long-term measurements of soil-plant-atmosphere variables at a forest site
- 1999
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Ingår i: Agricultural and Forest Meteorology. - 0168-1923 .- 1873-2240. ; 98-99, s. 53-73
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Tidskriftsartikel (refereegranskat)abstract
- It is a major challenge in modem science to decrease the uncertainty in predictions of global climate change. One of the largest uncertainties in present-day global climate models resides with the understanding of processes in the soil-vegetation-atmosphere-transfer (SVAT) system. Continuous, long-term data are needed in order to correctly quantify balances of water, energy and CO2 in this system and to correctly model it. It is the objective of this paper to demonstrate how a combined system of existing sensor, computer, and network technologies could be set up to provide continuous and reliable long-term SVAT-process data from a forested site under almost all environmental conditions. The Central Tower Site (CTS) system was set up in 1993-1994 in a 25 m high boreal forest growing on a highly heterogeneous till soil with a high content of stones and blocks. It has successfully monitored relevant states and fluxes in the system, such as atmospheric fluxes of momentum, heat, water vapour and CO2, atmospheric profiles of temperature, water vapour, CO2, short-and long-wave radiation, heat storage in soil and trees, sap-dow and a variety of ecophysiological properties, soil-water contents and tensions, and groundwater levels, rainfall and throughfall. System uptime has been more than 90% for most of its components during the first 5 years of operation. Results from the first 5 years of operation include e.g., budgets for energy, water and CO2, information on important but rarely occurring events such as evaporation from snow-covered canopies, and reactions of the forest to extreme drought. The carbon budget shows that the forest may be a sink of carbon although it is still growing. The completeness of the data has made it possible to test the internal consistency of SVAT models. The pioneering set-up at the CTS has been adopted by a large number of SVAT-monitoring sites around the world. Questions concerning tower maintenance, long-term calibration plans, maintenance of sensors and data-collection system, and continuous development of the computer network to keep it up to date are, however, only partly of interest as a research project in itself. It is thus difficult to get it funded from usual research-funding agencies. The full value of data generated by the CTS system can best be appreciated after a decade or more of continuous operation. Main uses of the data would be to evaluate how SVAT models handle the natural variability of climate conditions, quantification of water. carbon and energy budgets during various weather conditions, rind development of new parameterisation schemes in global and regional climate models.
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| 9. |
- Lundin, S.E., et al.
(författare)
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Solvärme och säsongslagring med borrhål i berg och llågtemperatur för bostadsområdet Anneberg, Danderyd : Förprojektering
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In the planning of a new housing area for 100 dwellings, a pre-design has been made for a solar heating plant. The aim of designing a layout, is to compare the solar system with more conventional heating systems. Developers and contractors are invited for turn-key tenders of the different systems. The single family houses, apartments and service premises in two storey, will have a total floor area of 9000 m{sup 2}. The heating demand is estimated to 1100 MWh/year (120 kWh/m{sup 2}) and the power to 450 kW. A new concept system is designed with low temperatures in all essential parts, but heat pumps are not needed. (1) Flat plate solar collectors, mean temperature 60 deg C; (2) Seasonal bore hole heat store in rock, temperature level 30-45 deg C; (3) Heat distribution network, working temperature 20-80 deg C; (4) Floor heating coils, temperature 25-32 deg C; (5) Peak electrical heaters in houses; (6) Solar DHW and auxiliary individual electrical final heaters. The system has only one general heat fluid with a mixture of water and glycol flowing through solar collectors, store, culverts and the floor heating coils. In all operation modes the heat carrier has the same flow direction and even act as a`buffer volume`. The bedrock consist of outcrops of granite and the GWL is at a depth of 4 m below the ground. In a 120 m investigation bore hole, a so called`Response test` is made in situ of the rock and the duct system. The obtained thermal results are: Conductivity{lambda}= 4.1 W/m,K, Capacity C 0.6 kWh/K, m{sup 3}, Resistance total of PEM-tubes and rock mass R= 0.02 K/(W/m). The investment cost have been calculated to 5.4 mil SEK ({approx} 0.7 mil USD) excl. culvert, floor heating system, DHW tanks/heaters. The annual capital and running costs are 0.73 mil SEK (0.1 mil USD), calculated with an interest rate of 6% over 25 years (0.078). The total system heating cost will be 0.68 SEK/kWh (0.1 USD/kWh). With received EU- and -governmental subsides up to 2.0 mil SEK the heating costs drop to 0.54 SEK/kWh (0.07 USD/kWh). Solar energy is by that means cost-effective to conventional alternatives as district heating, bio-fuel block centrals, ground heat pumps or 100% electrical heating. The solar heating project seems in all respects possible to carry through - but the final decision is taken of the market response
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| 10. |
- Nilsson, H., et al.
(författare)
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Investigation of the influence of magnetic anomalies on ion distributions at Mars
- 2006
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Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 126:1-4, s. 355-372
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Tidskriftsartikel (refereegranskat)abstract
- Using data from the Mars Express Ion Mass Analyzer (IMA) we investigate the distribution of ion beams of planetary origin and search for an influence from Mars crustal magnetic anomalies. We have concentrated on ion beams observed inside the induced magnetosphere boundary (magnetic pile-up boundary). Some north-south asymmetry is seen in the data, but no longitudinal structure resembling that of the crustal anomalies. Comparing the occurrence rate of ion beams with magnetic field strength at 400 km altitude below the spacecraft (using statistical Mars Global Surveyor results) shows a decrease of the occurrence rate for modest (< 40 nT) magnetic fields. Higher magnetic field regions (above 40 nT at 400 km) are sampled so seldom that the statistics are poor but the data is consistent with some ion outflow events being closely associated with the stronger anomalies. This ion flow does not significantly affect the overall distribution of ion beams around Mars.
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