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| 9. |
- Duarte-Cabral, A., et al.
(författare)
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The SEDIGISM survey: Molecular clouds in the inner Galaxy
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:3, s. 3027-3049
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Forskningsöversikt (refereegranskat)abstract
- We use the 13CO(2-1) emission from the SEDIGISM (Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) high-resolution spectral-line survey of the inner Galaxy, to extract the molecular cloud population with a large dynamic range in spatial scales, using the Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) algorithm. This work compiles a cloud catalogue with a total of 10 663 molecular clouds, 10 300 of which we were able to assign distances and compute physical properties. We study some of the global properties of clouds using a science sample, consisting of 6664 well-resolved sources and for which the distance estimates are reliable. In particular, we compare the scaling relations retrieved from SEDIGISM to those of other surveys, and we explore the properties of clouds with and without high-mass star formation. Our results suggest that there is no single global property of a cloud that determines its ability to form massive stars, although we find combined trends of increasing mass, size, surface density, and velocity dispersion for the sub-sample of clouds with ongoing high-mass star formation. We then isolate the most extreme clouds in the SEDIGISM sample (i.e. clouds in the tails of the distributions) to look at their overall Galactic distribution, in search for hints of environmental effects. We find that, for most properties, the Galactic distribution of the most extreme clouds is only marginally different to that of the global cloud population. The Galactic distribution of the largest clouds, the turbulent clouds and the high-mass star-forming clouds are those that deviate most significantly from the global cloud population. We also find that the least dynamically active clouds (with low velocity dispersion or low virial parameter) are situated further afield, mostly in the least populated areas. However, we suspect that part of these trends may be affected by some observational biases (such as completeness and survey limitations), and thus require further follow up work in order to be confirmed.
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| 10. |
- Schuller, F., et al.
(författare)
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The SEDIGISM survey: First Data Release and overview of the Galactic structure
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:3, s. 3064-3082
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Tidskriftsartikel (refereegranskat)abstract
- The SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic InterstellarMedium) survey used the APEX telescope to map 84 deg(2) of the Galactic plane between l = -60 degrees and +31 degrees in several molecular transitions, including (CO)-C-13(2 - 1) and (CO)-O-18(2 - 1), thus probing the moderately dense (similar to 10(3) cm(-3)) component of the interstellar medium. With an angular resolution of 30 arcsec and a typical 1 sigma sensitivity of 0.8-1.0K at 0.25 km s(-1) velocity resolution, it gives access to a wide range of structures, from individual star-forming clumps to giant molecular clouds and complexes. The coverage includes a good fraction of the first and fourth Galactic quadrants, allowing us to constrain the large-scale distribution of cold molecular gas in the inner Galaxy. In this paper, we provide an updated overview of the full survey and the data reduction procedures used. We also assess the quality of these data and describe the data products that are being made publicly available as part of this First Data Release (DR1). We present integrated maps and position-velocity maps of the molecular gas and use these to investigate the correlation between the molecular gas and the large-scale structural features of the Milky Way such as the spiral arms, Galactic bar and Galactic Centre. We find that approximately 60 per cent of the molecular gas is associated with the spiral arms and these appear as strong intensity peaks in the derived Galactocentric distribution. We also find strong peaks in intensity at specific longitudes that correspond to the Galactic Centre and well-known star-forming complexes, revealing that the 13CO emission is concentrated in a small number of complexes rather than evenly distributed along spiral arms.
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| 11. |
- Akiyama, Kazunori, et al.
(författare)
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First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration
- 2022
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
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Tidskriftsartikel (refereegranskat)abstract
- We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5-11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of similar to 50 mu as, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.
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| 12. |
- Angelopoulus, M., et al.
(författare)
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Physical properties of sea ice cores from site MCS_FYI measured on legs 1 to 3 of the MOSAiC expedition.
- 2022
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Ingår i: PANGAEA.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present sea ice temperature and salinity data from first-year ice (FYI) and second-year ice (SYI) relevant to the temporal development of sea ice permeability and brine drainage efficiency from the early growth phase in October 2019 to the onset of spring warming in May 2020. Our dataset was collected in the central Arctic Ocean during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 to 2020. MOSAiC was an international transpolar drift expedition in which the German icebreaker RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. In October 2019, RV Polarstern moored to an ice floe in the Siberian sector of the Arctic at 85 degrees north and 137 degrees east to begin the drift towards the North Pole and the Fram Strait via the Transpolar Drift Stream. The data presented here were collected during the first three legs of the expedition, so all the coring activities took place on the same floe. The end dates of legs 1, 2, and 3 were 13 December, 24 February, and 4 June, respectively. The dataset contributed to a baseline study entitled, Deciphering the properties of different Arctic ice types during the growth phase of the MOSAiC floes: Implications for future studies. The study highlights downward directed gas pathways in FYI and SYI by inferring sea ice permeability and potential brine release from several time series of temperature and salinity measurements. The physical properties presented in this paper lay the foundation for subsequent analyses on actual gas contents measured in the ice cores, as well as air-ice and ice-ocean gas fluxes. Sea ice cores were collected with a Kovacs Mark II 9 cm diameter corer. To measure ice temperatures, about 4.5 cm deep holes were drilled into the core (intervals varied by site and leg) . The temperatures were measured by a digital thermometer within minutes after the cores were retrieved. The ice cores were placed into pre-labelled plastic sleeves sealed at the bottom end. The ice cores were transported to RV Polarstern and stored in a -20 degrees Celsius freezer. Each of the cores was sub-sampled, melted at room temperature, and processed for salinity within one or two days. The practical salinity was estimated by measuring the electrical conductivity and temperature of the melted samples using a WTW Cond 3151 salinometer equipped with a Tetra-Con 325 four-electrode conductivity cell. The practical salinity represents the the salinity estimated from the electrical conductivity of the solution. The dataset also contains derived variables, including sea ice density, brine volume fraction, and the Rayleigh number.
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| 13. |
- Angelopoulus, M., et al.
(författare)
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Physical properties of sea ice cores from site MCS-SYI measured on legs 1 to 3 of the MOSAiC expedition
- 2022
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Ingår i: PANGAEA.
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We present sea ice temperature and salinity data from first-year ice (FYI) and second-year ice (SYI) relevant to the temporal development of sea ice permeability and brine drainage efficiency from the early growth phase in October 2019 to the onset of spring warming in May 2020. Our dataset was collected in the central Arctic Ocean during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Expedition in 2019 to 2020. MOSAiC was an international transpolar drift expedition in which the German icebreaker RV Polarstern anchored into an ice floe to gain new insights into Arctic climate over a full annual cycle. In October 2019, RV Polarstern moored to an ice floe in the Siberian sector of the Arctic at 85 degrees north and 137 degrees east to begin the drift towards the North Pole and the Fram Strait via the Transpolar Drift Stream. The data presented here were collected during the first three legs of the expedition, so all the coring activities took place on the same floe. The end dates of legs 1, 2, and 3 were 13 December, 24 February, and 4 June, respectively. The dataset contributed to a baseline study entitled, Deciphering the properties of different Arctic ice types during the growth phase of the MOSAiC floes: Implications for future studies. The study highlights downward directed gas pathways in FYI and SYI by inferring sea ice permeability and potential brine release from several time series of temperature and salinity measurements. The physical properties presented in this paper lay the foundation for subsequent analyses on actual gas contents measured in the ice cores, as well as air-ice and ice-ocean gas fluxes. Sea ice cores were collected with a Kovacs Mark II 9 cm diameter corer. To measure ice temperatures, about 4.5 cm deep holes were drilled into the core (intervals varied by site and leg) . The temperatures were measured by a digital thermometer within minutes after the cores were retrieved. The ice cores were placed into pre-labelled plastic sleeves sealed at the bottom end. The ice cores were transported to RV Polarstern and stored in a -20 degrees Celsius freezer. Each of the cores was sub-sampled, melted at room temperature, and processed for salinity within one or two days. The practical salinity was estimated by measuring the electrical conductivity and temperature of the melted samples using a WTW Cond 3151 salinometer equipped with a Tetra-Con 325 four-electrode conductivity cell. The practical salinity represents the the salinity estimated from the electrical conductivity of the solution. The dataset also contains derived variables, including sea ice density, brine volume fraction, and the Rayleigh number.
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| 14. |
- Andersson, Agneta, et al.
(författare)
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DNA-streckkodning av marina växtplankton : Ett nytt verktyg i miljöövervakningen
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Växtplankton utgör grunden i den marina näringsväven och används världen över för att bestämma miljöstatus i hav och sjöar. De ingår exempelvis som en kvalitetsfaktor i EU:s vattendirektiv och havsmiljödirektiv. Det finns långa tidsserier av växtplanktonövervakning där analyserna utförts med mikroskopi. Det sker nu en snabb internationell utveckling av DNA-metoder för att övervaka växtplankton. Målsättningen med detta projekt var att utveckla en praktisk och robust DNA analysmetod som kan implementeras i svensk marin miljöövervakning. Vårt tillvägagångssätt var att följa med på ordinarie marina miljöövervakningsexpeditioner under ett års tid (2019–2020) och ta parallella havsvattenprov för så kallad DNA-streckkodning av växtplankton. Sammanlagt tog vi prov vid 19 övervakningsstationer som var spridda från Bottenviken i norr till Skagerrak i söder. Provtagningsfrekvensen var cirka 1 gång per månad. Praktiska metoder utarbetades för fältprovtagning, DNA-extraktion, sekvensering, bioinformatisk analys och taxonomisk annotering. Vi har även tagit fram system för datahantering hos nationell datavärd och gett förslag på en ny datatyp för nationellt datavärdskap för marinbiologi och oceanografi vid Svenskt Oceanografiskt Datacentrum (https://sharkweb. smhi.se/hamta-data/). En viktig del har varit att jämföra resultaten av DNA-streckkodning och mikroskopi. Resultaten visar att DNA-streckkodning ger ungefär dubbelt så högt biodiversitetsmått än mikroskopering, även om det skiljer sig åt mellan olika grupper av växtplankton. För att undersöka om DNA-streckkodning kan användas för kvantitativ analys tillsatte vi en intern standard till proverna bestående av syntetiskt DNA, men eftersom resultatet varierade så behöver man arbeta vidare med detta. Den relativa fördelningen av vanliga eukaryota växtplanktongrupper visade sig ha relativt bra överensstämmelse mellan DNA-streckkodning och mikroskopimåttet kolbiomassa, medan biovolym och abundans skiljde sig åt mer. DNA-streckkodning visade sig ge detaljerade utbredningsmönster av skadliga alger, till exempel för släktet Prymnesium bland häftalgerna (Coccolithophyceae). Vi har inom projektet kunnat utvärdera ekologiska drivkrafter för växtplanktonsamhällets diversitet och artsammansättning, genom att miljöövervakningen mäter många fysikalisk-kemiska parametrar. Både salthalt och närsalter visade sig ha stor inverkan på växtplanktonsamhällets sammansättning och diversitet. Sammanfattningsvis ser vi att den framtagna DNA-streckkodningsmetoden skulle vara ett bra komplement till den etablerade växtplanktonövervakningen.
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| 15. |
- Andersson, Robin, 1986, et al.
(författare)
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Integrated analysis of dynamic vehicle-track interaction and plasticity induced damage in the presence of squat defects
- 2015
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Ingår i: Proceedings of the 10th International International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Colorado Springs, USA, August-September 2015.
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Konferensbidrag (refereegranskat)abstract
- Despite significant efforts, the mechanisms behind the formation of squats – a form of rolling contact fatigue damage – are not fully understood. This study employs numerical simulations to investigate the propensity of squat initiation in the vicinity of small, isolated rail surface irregularities. Time domain dynamic vehicle–track interaction analysis is used to obtain wheel–rail contact stress distributions, which are mapped onto a continuum finite element model that accounts for plastic deformation of the rail material. The evaluated stress and strain fields are quantified using two RCF impact measures: accumulated effective strain and the Jiang-Sehitoglu multiaxial low cycle fatigue parameter. It is shown that the RCF impact increases with increasing size of the surface irregularity and that clustering of irregularities might strongly promote RCF. The friction coefficient is identified as a very influential parameter. Further, the effect of variations in friction along the rail is evaluated. It is shown that a short rail section of low friction results in fairly high RCF impact.
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| 16. |
- Belitsky, Victor, 1955, et al.
(författare)
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SEPIA - A new single pixel receiver at the APEX telescope
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 612
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Tidskriftsartikel (refereegranskat)abstract
- Context. We describe the new Swedish-ESO PI Instrument for APEX (SEPIA) receiver, which was designed and built by the Group for Advanced Receiver Development (GARD), at Onsala Space Observatory (OSO) in collaboration with ESO. It was installed and commissioned at the APEX telescope during 2015 with an ALMA Band 5 receiver channel and updated with a new frequency channel (ALMA Band 9) in February 2016. Aim. This manuscript aims to provide, for observers who use the SEPIA receiver, a reference in terms of the hardware description, optics and performance as well as the commissioning results. Methods. Out of three available receiver cartridge positions in SEPIA, the two current frequency channels, corresponding to ALMA Band 5, the RF band 158-211 GHz, and Band 9, the RF band 600-722 GHz, provide state-of-the-art dual polarization receivers. The Band 5 frequency channel uses 2SB SIS mixers with an average SSB noise temperature around 45 K with IF (intermediate frequency) band 4-8 GHz for each sideband providing total 4 × 4 GHz IF band. The Band 9 frequency channel uses DSB SIS mixers with a noise temperature of 75-125 K with IF band 4-12 GHz for each polarization. Results. Both current SEPIA receiver channels are available to all APEX observers.
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| 17. |
- Carlberger, Andreas, 1992, et al.
(författare)
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Numerical prediction of rail corrugation growth on curves
- 2016
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Ingår i: Proceedings of the 19h Nordic Seminar on Railway Technology, September 14 - 15, Luleå, Sweden (2016).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Rail corrugation (periodic surface irregularities at distinct wavelengths) is a problem experienced by many railway networks worldwide. Corrugation induces a pronounced dynamic wheel‒rail contact loading that leads to increased generation of noise and in severe cases even damage to vehicle and track components. The large magnitude creep forces and sliding between wheel and rail make corrugation especially prone to develop on curved track. The current work summarizes the results from a Master Thesis project performed in collaboration between Chalmers, ÅF Industry, Bombardier Transportation and Stockholm Public Transport. A time-domain model for the prediction of long-term growth of rail roughness has been developed, see Figure 1. Dynamic vehicle‒track interaction in a broad frequency range (at least up to 300 Hz) is simulated using the commercial software SIMPACK. Wheelset structural flexibility is accounted for by using modal parameters calculated for a finite element model. Non-Hertzian and non-steady wheel‒rail contact and associated generation of wear are calculated in a post-processing step in the software Matlab. Archard’s law is applied to model the sliding wear. A large number of train passages is accounted for by recurrent updating of the rail surface irregularity based on the calculated wear depth. The proposed prediction model is applied to investigate a curve on the Stockholm metro network exposed to severe corrugation growth.
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| 18. |
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| 19. |
- Dawson, H. M., et al.
(författare)
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Large Diversity in Nitrogen- and Sulfur-Containing Compatible Solute Profiles in Polar and Temperate Diatoms
- 2020
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Ingår i: Integrative and Comparative Biology. - : OXFORD UNIV PRESS INC. - 1540-7063 .- 1557-7023. ; 60:6, s. 1401-1413
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Tidskriftsartikel (refereegranskat)abstract
- Intense bottom-ice algal blooms, often dominated by diatoms, are an important source of food for grazers, organic matter for export during sea ice melt, and dissolved organic carbon. Sea-ice diatoms have a number of adaptations, including accumulation of compatible solutes, that allows them to inhabit this highly variable environment characterized by extremes in temperature, salinity, and light. In addition to protecting them from extreme conditions, these compounds present a labile, nutrient-rich source of organic matter, and include precursors to climate active compounds (e.g., dimethyl sulfide [DMS]), which are likely regulated with environmental change. Here, intracellular concentrations of 45 metabolites were quantified in three sea-ice diatom species and were compared to two temperate diatom species, with a focus on compatible solutes and free amino acid pools. There was a large diversity of metabolite concentrations between diatoms with no clear pattern identifiable for sea-ice species. Concentrations of some compatible solutes (isethionic acid, homarine) approached 1 M in the sea-ice diatoms, Fragilariopsis cylindrus and Navicula cf. perminuta, but not in the larger sea-ice diatom, Nitzschia lecointei or in the temperate diatom species. The differential use of compatible solutes in sea-ice diatoms suggests different adaptive strategies and highlights which small organic compounds may be important in polar biogeochemical cycles.
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| 20. |
- Kelpsiene, Egle, et al.
(författare)
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Long-term exposure to nanoplastics reduces life-time in Daphnia magna
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Plastics are widely used in todays society leading to an accelerating amount of plastic waste entering natural ecosystems. Over time these waste products degrade to micro- and, eventually, nanoplastic particles. Therefore, the break-down of plastics may become a critical threat to aquatic ecosystems and several short term studies have demonstrated acute toxicity of nanoplastics on aquatic organisms. However, our knowledge about effects of chronic or life-time exposure on freshwater invertebrates remains elusive. Here, we demonstrate results from life-time exposure (103 days) of a common freshwater invertebrate, Daphnia magna, exposed to sub-lethal concentrations of polystyrene nanoparticles. 53 nm positively charged aminated polystyrene particles were lethal at concentration of 0.32 mg/L which is two magnitudes lower than previously used concentrations in short-term (24 h) tests. At this concentration the life-time of individuals was shortened almost three times. Negatively charged carboxylated 26 and 62 nm polystyrene particles, previously demonstrated to be non-toxic at 25 and 50 mg/L concentrations in short-term tests, were toxic to D. magna at all concentrations used in our long-term study. Although total reproductive output was not significantly affected at increasing concentrations of polystyrene nanoparticles, there was a decreasing trend in the number of offspring over their life-time. Hence, in order to understand how the potential future environmental problem of nanoplastic particles may affect biota, long-term or life-time studies resembling environmental concentrations should be performed in order to provide information for predictions of future scenarios in natural aquatic environments.
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| 21. |
- Kelpsiene, Egle, et al.
(författare)
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Review of ecotoxicological studies of widely used polystyrene nanoparticles
- 2022
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Ingår i: Environmental Science: Processes & Impacts. - 2050-7895. ; 24:1, s. 8-16
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Forskningsöversikt (refereegranskat)abstract
- With polystyrene nanoparticles being widely used in various applications, there is a great need for deeper knowledge on the safety, fate and biological effects of these particles on both individual living organisms and the whole ecosystems. Due to this, there is a growing interest in performing ecotoxicological studies using model plastic nanoparticles, and consequently it generates an increasing number of published papers describing the negative impact on wildlife caused by such nanoparticles. Polystyrene is the most studied nanosized plastic, therefore this review focuses on research conducted with manufactured polystyrene nanoparticles. The aim of the present article is to provide a critical methodological outline of the existing ecotoxicological studies on the effects of polystyrene nanoparticles on aquatic organisms. Going through the published articles, we noted that particle characterization especially in the test medium, can be improved. The analysis also highlights the importance of purifying the polystyrene nanoparticles before studying its toxicity. Furthermore, the size characterization of such nanoparticles is underemphasized, and in future studies, authors should consider including more techniques to achieve this goal. Finally, short-term or direct exposure scenarios do not add the most environmentally relevant knowledge in terms of the toxicity caused by polystyrene nanoparticles.
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| 22. |
- Latz, Meike, et al.
(författare)
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A comprehensive dataset on spatiotemporal variation of microbial plankton communities in the Baltic Sea
- 2024
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Ingår i: Scientific Data. - : Springer Nature. - 2052-4463. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The Baltic Sea is one of the largest brackish water environments on earth and is characterised by pronounced physicochemical gradients and seasonal dynamics. Although the Baltic Sea has a long history of microscopy-based plankton monitoring, DNA-based metabarcoding has so far mainly been limited to individual transect cruises or time-series of single stations. Here we report a dataset covering spatiotemporal variation in prokaryotic and eukaryotic microbial communities and physicochemical parameters. Within 13-months between January 2019 and February 2020, 341 water samples were collected at 22 stations during monthly cruises along the salinity gradient. Both salinity and seasonality are strongly reflected in the data. Since the dataset was generated with both metabarcoding and microscopy-based methods, it provides unique opportunities for both technical and ecological analyses, and is a valuable biodiversity reference for future studies, in the prospect of climate change.
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| 23. |
- Li, Xin, 1985, et al.
(författare)
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Simulation of vertical dynamic vehicle-track interaction in a railway crossing using Green's functions
- 2017
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 410, s. 318-329
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Tidskriftsartikel (refereegranskat)abstract
- Vertical dynamic vehicle-track interaction in the through route of a railway crossing is simulated in the time domain based on a Green's function approach for the track in combination with an implementation of Kalker's variational method to solve the non-Hertzian, and potentially multiple, wheel-rail contact. The track is described by a linear, three-dimensional and non-periodic finite element model of a railway turnout accounting for the variations in rail cross-sections and sleeper lengths, and including baseplates and resilient elements. To reduce calculation time due to the complexity of the track model, involving a large number of elements and degrees-of-freedom, a complex-valued modal superposition with a truncated mode set is applied before the impulse response functions are calculated at various positions along the crossing panel. The variation in three-dimensional contact geometry of the crossing and wheel is described by linear surface elements. In each time step of the contact detection algorithm, the lateral position of the wheelset centre is prescribed but the contact positions on wheel and rail are not, allowing for an accurate prediction of the wheel transition between wing rail and crossing rail. The method is demonstrated by calculating the wheel-rail impact load and contact stress distribution for a nominal S1002 wheel profile passing over a nominal crossing geometry. A parameter study is performed to determine the influence of vehicle speed, rail pad stiffness, lateral wheelset position and wheel profile on the impact load generated at the crossing. It is shown that the magnitude of the impact load is more influenced the wheel-rail contact geometry than by the selection of rail pad stiffness.
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| 24. |
- Mock, Thomas, et al.
(författare)
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Multiomics in the central Arctic Ocean for benchmarking biodiversity change
- 2022
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Ingår i: PLoS biology. - : Public Library of Science (PLoS). - 1544-9173 .- 1545-7885. ; 20:10
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Tidskriftsartikel (refereegranskat)abstract
- Multiomics approaches need to be applied in the central Arctic Ocean to benchmark biodiversity change and to identify novel species and their genes. As part of MOSAiC, EcoOmics will therefore be essential for conservation and sustainable bioprospecting in one of the least explored ecosystems on Earth.
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| 25. |
- Nielsen, Jens, 1963, et al.
(författare)
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Switch panel design based on simulation of accumulated rail damage in a railway turnout
- 2015
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Ingår i: Proceedings of the 10th International International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, Colorado Springs, USA, August-September 2015.
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Konferensbidrag (refereegranskat)abstract
- A methodology for numerical prediction of accumulated rail damage in railway turnouts is presented. Based onsimulation of dynamic vehicle‒track interaction followed by a discretisation of the conditions in each wheel‒railcontact, distributions of rail wear are calculated by the Archard model of sliding wear, while surface initiated rollingcontact fatigue (RCF) damage is evaluated by the Palmgren-Miner rule and an index building on shakedown theory.Partial slip in the wheel‒rail contacts and variable amplitude loading are considered. For freight traffic in the divergingroute, the influence of rail inclination and switch rail height on damage in the switch panel is investigated in ademonstration example. Two-point contact situations with one contact on the switch rail and one on top of the stock rail induce relative motion and slip between wheel and rail leading to high energy dissipation. In agreement with fieldobservations, it is concluded that wear is the dominating damage mechanism on the gauge side of the switch rail whilethe risk for RCF is higher on the crowns of the switch and stock rails. For accurate prediction of rail life for givencombinations of wheel/rail materials and traffic conditions, the methodology needs to be calibrated by fieldmeasurements.
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