| 1. |
- Fray, Nicolas, et al.
(author)
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High-molecular-weight organic matter in the particles of comet 67P/Churyumov–Gerasimenko
- 2016
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In: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 538:7623, s. 72-74
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Journal article (peer-reviewed)abstract
- The presence of solid carbonaceous matter in cometary dust was established by the detection of elements such as carbon, hydrogen, oxygen and nitrogen in particles from comet 1P/Halley1, 2. Such matter is generally thought to have originated in the interstellar medium3, but it might have formed in the solar nebula—the cloud of gas and dust that was left over after the Sun formed4. This solid carbonaceous material cannot be observed from Earth, so it has eluded unambiguous characterization5. Many gaseous organic molecules, however, have been observed6, 7, 8, 9; they come mostly from the sublimation of ices at the surface or in the subsurface of cometary nuclei8. These ices could have been formed from material inherited from the interstellar medium that suffered little processing in the solar nebula10. Here we report the in situ detection of solid organic matter in the dust particles emitted by comet 67P/Churyumov–Gerasimenko; the carbon in this organic material is bound in very large macromolecular compounds, analogous to the insoluble organic matter found in the carbonaceous chondrite meteorites11, 12. The organic matter in meteorites might have formed in the interstellar medium and/or the solar nebula, but was almost certainly modified in the meteorites’ parent bodies11. We conclude that the observed cometary carbonaceous solid matter could have the same origin as the meteoritic insoluble organic matter, but suffered less modification before and/or after being incorporated into the comet.
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| 2. |
- Bacquart, Thomas, et al.
(author)
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Hydrogen fuel quality from two main production processes : Steam methane reforming and proton exchange membrane water electrolysis
- 2019
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In: Journal of Power Sources. - : Elsevier B.V.. - 0378-7753 .- 1873-2755. ; 444
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Journal article (peer-reviewed)abstract
- The absence of contaminants in the hydrogen delivered at the hydrogen refuelling station is critical to ensure the length life of FCEV. Hydrogen quality has to be ensured according to the two international standards ISO 14687–2:2012 and ISO/DIS 19880-8. Amount fraction of contaminants from the two hydrogen production processes steam methane reforming and PEM water electrolyser is not clearly documented. Twenty five different hydrogen samples were taken and analysed for all contaminants listed in ISO 14687-2. The first results of hydrogen quality from production processes: PEM water electrolysis with TSA and SMR with PSA are presented. The results on more than 16 different plants or occasions demonstrated that in all cases the 13 compounds listed in ISO 14687 were below the threshold of the international standards. Several contaminated hydrogen samples demonstrated the needs for validated and standardised sampling system and procedure. The results validated the probability of contaminants presence proposed in ISO/DIS 19880-8. It will support the implementation of ISO/DIS 19880-8 and the development of hydrogen quality control monitoring plan. It is recommended to extend the study to other production method (i.e. alkaline electrolysis), the HRS supply chain (i.e. compressor) to support the technology growth.
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| 3. |
- de la Vara, Jose Luis, et al.
(author)
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A Proposal for the Classification of Methods for Verification and Validation of Safety, Cybersecurity, and Privacy of Automated Systems
- 2021
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In: 14th International Conference on the Quality of Information and Communications Technology (QUATIC 2021).
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Conference paper (peer-reviewed)abstract
- As our dependence on automated systems grows, so does the need for guaranteeing their safety, cybersecurity, and privacy (SCP). Dedicated methods for verification and validation (V&V) must be used to this end and it is necessary that the methods and their characteristics can be clearly differentiated. This can be achieved via method classifications. However, we have experienced that existing classifications are not suitable to categorise V&V methods for SCP of automated systems. They do not pay enough attention to the distinguishing characteristics of this system type and of these quality concerns. As a solution, we present a new classification developed in the scope of a large-scale industry-academia project. The classification considers both the method type, e.g., testing, and the concern addressed, e.g., safety. Over 70 people have successfully used the classification on 53 methods. We argue that the classification is a more suitable means to categorise V&V methods for SCP of automated systems and that it can help other researchers and practitioners.
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| 4. |
- Fischer, Katharina, et al.
(author)
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Field-experience based root-cause analysis of power-converter failure in wind turbines
- 2015
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In: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers Inc.. - 0885-8993 .- 1941-0107. ; 30:5, s. 2481-2492
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Journal article (peer-reviewed)abstract
- The frequent power-converter failure experienced in wind turbines has a strong economic impact through both the related turbine unavailability and the maintenance cost. Up to now, the prevailing mechanisms and causes underlying the converter failure in wind turbines are mostly unknown. Their identification is, however, a prerequisite for the development of effective solutions. This paper describes a multitrack empirical approach to failure analysis including systematic field-data evaluation, exploration of the real converter operating environment, and postoperational laboratory investigation of converter hardware. The analysis is carried out for two widely used multi-MW wind turbines with low-voltage, insulated-gate bipolar transistor-based converters (topology 1: doubly fed induction generator with partially rated converter, topology 2: induction generator with fully rated converter). The findings suggest that the principle failure mechanisms of power electronics found in other applications, namely solder degradation and bond-wire damage, play a minor role in the investigated types of wind turbines. Instead, the analysis reveals indications of insufficient protection of the converter hardware against the environment (salt, condensation, and insects) as well as indications of electrical overstress.
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| 5. |
- Hilchenbach, M., et al.
(author)
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COMET 67P/CHURYUMOV-GERASIMENKO : CLOSE-UP on DUST PARTICLE FRAGMENTS
- 2016
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In: Astrophysical Journal Letters. - : Institute of Physics Publishing (IOPP). - 2041-8205 .- 2041-8213. ; 816:2
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Journal article (peer-reviewed)abstract
- The COmetary Secondary Ion Mass Analyser instrument on board ESA's Rosetta mission has collected dust particles in the coma of comet 67P/Churyumov-Gerasimenko. During the early-orbit phase of the Rosetta mission, particles and particle agglomerates have been imaged and analyzed in the inner coma at distances between 100 km and 10 km off the cometary nucleus and at more than 3 AU from the Sun. We identified 585 particles of more than 14 μm in size. The particles are collected at low impact speeds and constitute a sample of the dust particles in the inner coma impacting and fragmenting on the targets. The sizes of the particles range from 14 μm up to sub-millimeter sizes and the differential dust flux size distribution is fitted with a power law exponent of -3.1. After impact, the larger particles tend to stick together, spread out or consist of single or a group of clumps, and the flocculent morphology of the fragmented particles is revealed. The elemental composition of the dust particles is heterogeneous and the particles could contain typical silicates like olivine and pyroxenes, as well as iron sulfides. The sodium to iron elemental ratio is enriched with regard to abundances in CI carbonaceous chondrites by a factor from ∼1.5 to ∼15. No clear evidence for organic matter has been identified. The composition and morphology of the collected dust particles appear to be similar to that of interplanetary dust particles.
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| 6. |
- Hilchenbach, Martin, et al.
(author)
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Mechanical and electrostatic experiments with dust particles collected in the inner coma of comet 67P by COSIMA onboard Rosetta
- 2017
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In: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 375:2097
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Journal article (peer-reviewed)abstract
- The in situ cometary dust particle instrument COSIMA (COmetary Secondary Ion Mass Analyser) onboard ESA's Rosetta mission has collected about 31 000 dust particles in the inner coma of comet 67P/Churyumov-Gerasimenko since August 2014. The particles are identified by optical microscope imaging and analysed by time-of-flight secondary ion mass spectrometry. After dust particle collection by low speed impact on metal targets, the collected particle morphology points towards four families of cometary dust particles. COSIMA is an in situ laboratory that operates remotely controlled next to the comet nucleus. The particles can be further manipulated within the instrument by mechanical and electrostatic means after their collection by impact. The particles are stored above 0°C in the instrument and the experiments are carried out on the refractory, ice-free matter of the captured cometary dust particles. An interesting particle morphology class, the compact particles, is not fragmented on impact. One of these particles was mechanically pressed and thereby crushed into large fragments. The particles are good electrical insulators and transform into rubble pile agglomerates by the application of an energetic indium ion beam during the secondary ion mass spectrometry analysis. This article is part of the themed issue 'Cometary science after Rosetta'. © 2017 The Authors.
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| 7. |
- Krüger, Harald, et al.
(author)
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COSIMA-Rosetta calibration for in situ characterization of 67P/Churyumov-Gerasimenko cometary inorganic compounds
- 2015
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In: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 117, s. 35-44
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Journal article (peer-reviewed)abstract
- COmetary Secondary Ion Mass Analyzer (COSIMA) is a time-of-flight secondary ion mass spectrometry (TOF-SIMS) instrument on board the Rosetta space mission. COSIMA has been designed to measure the composition of cometary dust particles. It has a mass resolution m/Δm of 1400 at mass 100 u, thus enabling the discrimination of inorganic mass peaks from organic ones in the mass spectra. We have evaluated the identification capabilities of the reference model of COSIMA for inorganic compounds using a suite of terrestrial minerals that are relevant for cometary science. Ground calibration demonstrated that the performances of the flight model were similar to that of the reference model. The list of minerals used in this study was chosen based on the mineralogy of meteorites, interplanetary dust particles and Stardust samples. It contains anhydrous and hydrous ferromagnesian silicates, refractory silicates and oxides (present in meteoritic Ca-Al-rich inclusions), carbonates, and Fe-Ni sulfides. From the analyses of these minerals, we have calculated relative sensitivity factors for a suite of major and minor elements in order to provide a basis for element quantification for the possible identification of major mineral classes present in the cometary particles.
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