1. |
- Adams, E. A. K., et al.
(författare)
-
First release of Apertif imaging survey data
- 2022
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 667
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Apertif is a phased-array feed system for the Westerbork Synthesis Radio Telescope, providing forty instantaneous beams over 300 MHz of bandwidth. A dedicated survey program utilizing this upgrade started on 1 July 2019, with the last observations taken on 28 February 2022. The imaging survey component provides radio continuum, polarization, and spectral line data. Aims. Public release of data is critical for maximizing the legacy of a survey. Toward that end, we describe the release of data products from the first year of survey operations, through 30 June 2020. In particular, we focus on defining quality control metrics for the processed data products. Methods. The Apertif imaging pipeline, Apercal, automatically produces non-primary beam corrected continuum images, polarization images and cubes, and uncleaned spectral line and dirty beam cubes for each beam of an Apertif imaging observation. For this release, processed data products are considered on a beam-by-beam basis within an observation. We validate the continuum images by using metrics that identify deviations from Gaussian noise in the residual images. If the continuum image passes validation, we release all processed data products for a given beam. We apply further validation to the polarization and line data products and provide flags indicating the quality of those data products. Results. We release all raw observational data from the first year of survey observations, for a total of 221 observations of 160 independent target fields, covering approximately one thousand square degrees of sky. Images and cubes are released on a per beam basis, and 3374 beams (of 7640 considered) are released. The median noise in the continuum images is 41.4 uJy beam(-1), with a slightly lower median noise of 36.9 uJy beam(-1) in the Stokes V polarization image. The median angular resolution is 11.6 ''/sin delta. The median noise for all line cubes, with a spectral resolution of 36.6 kHz, is 1.6 mJy beam(-1), corresponding to a 3-sigma H i column density sensitivity of 1.8 x 10(20) atoms cm(-2) over 20 km s(-1) (for a median angular resolution of 24 '' x 15 ''). Line cubes at lower frequency have slightly higher noise values, consistent with the global RFI environment and overall Apertif system performance. We also provide primary beam images for each individual Apertif compound beam. The data are made accessible using a Virtual Observatory interface and can be queried using a variety of standard tools.
|
|
2. |
- Backes, Claudia, et al.
(författare)
-
Production and processing of graphene and related materials
- 2020
-
Ingår i: 2D Materials. - : IOP Publishing. - 2053-1583. ; 7:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present an overview of the main techniques for production and processing of graphene and related materials (GRMs), as well as the key characterization procedures. We adopt a 'hands-on' approach, providing practical details and procedures as derived from literature as well as from the authors' experience, in order to enable the reader to reproduce the results. Section I is devoted to 'bottom up' approaches, whereby individual constituents are pieced together into more complex structures. We consider graphene nanoribbons (GNRs) produced either by solution processing or by on-surface synthesis in ultra high vacuum (UHV), as well carbon nanomembranes (CNM). Production of a variety of GNRs with tailored band gaps and edge shapes is now possible. CNMs can be tuned in terms of porosity, crystallinity and electronic behaviour. Section II covers 'top down' techniques. These rely on breaking down of a layered precursor, in the graphene case usually natural crystals like graphite or artificially synthesized materials, such as highly oriented pyrolythic graphite, monolayers or few layers (FL) flakes. The main focus of this section is on various exfoliation techniques in a liquid media, either intercalation or liquid phase exfoliation (LPE). The choice of precursor, exfoliation method, medium as well as the control of parameters such as time or temperature are crucial. A definite choice of parameters and conditions yields a particular material with specific properties that makes it more suitable for a targeted application. We cover protocols for the graphitic precursors to graphene oxide (GO). This is an important material for a range of applications in biomedicine, energy storage, nanocomposites, etc. Hummers' and modified Hummers' methods are used to make GO that subsequently can be reduced to obtain reduced graphene oxide (RGO) with a variety of strategies. GO flakes are also employed to prepare three-dimensional (3d) low density structures, such as sponges, foams, hydro- or aerogels. The assembly of flakes into 3d structures can provide improved mechanical properties. Aerogels with a highly open structure, with interconnected hierarchical pores, can enhance the accessibility to the whole surface area, as relevant for a number of applications, such as energy storage. The main recipes to yield graphite intercalation compounds (GICs) are also discussed. GICs are suitable precursors for covalent functionalization of graphene, but can also be used for the synthesis of uncharged graphene in solution. Degradation of the molecules intercalated in GICs can be triggered by high temperature treatment or microwave irradiation, creating a gas pressure surge in graphite and exfoliation. Electrochemical exfoliation by applying a voltage in an electrolyte to a graphite electrode can be tuned by varying precursors, electrolytes and potential. Graphite electrodes can be either negatively or positively intercalated to obtain GICs that are subsequently exfoliated. We also discuss the materials that can be amenable to exfoliation, by employing a theoretical data-mining approach. The exfoliation of LMs usually results in a heterogeneous dispersion of flakes with different lateral size and thickness. This is a critical bottleneck for applications, and hinders the full exploitation of GRMs produced by solution processing. The establishment of procedures to control the morphological properties of exfoliated GRMs, which also need to be industrially scalable, is one of the key needs. Section III deals with the processing of flakes. (Ultra)centrifugation techniques have thus far been the most investigated to sort GRMs following ultrasonication, shear mixing, ball milling, microfluidization, and wet-jet milling. It allows sorting by size and thickness. Inks formulated from GRM dispersions can be printed using a number of processes, from inkjet to screen printing. Each technique has specific rheological requirements, as well as geometrical constraints. The solvent choice is critical, not only for the GRM stability, but also in terms of optimizing printing on different substrates, such as glass, Si, plastic, paper, etc, all with different surface energies. Chemical modifications of such substrates is also a key step. Sections IV-VII are devoted to the growth of GRMs on various substrates and their processing after growth to place them on the surface of choice for specific applications. The substrate for graphene growth is a key determinant of the nature and quality of the resultant film. The lattice mismatch between graphene and substrate influences the resulting crystallinity. Growth on insulators, such as SiO2, typically results in films with small crystallites, whereas growth on the close-packed surfaces of metals yields highly crystalline films. Section IV outlines the growth of graphene on SiC substrates. This satisfies the requirements for electronic applications, with well-defined graphene-substrate interface, low trapped impurities and no need for transfer. It also allows graphene structures and devices to be measured directly on the growth substrate. The flatness of the substrate results in graphene with minimal strain and ripples on large areas, allowing spectroscopies and surface science to be performed. We also discuss the surface engineering by intercalation of the resulting graphene, its integration with Si-wafers and the production of nanostructures with the desired shape, with no need for patterning. Section V deals with chemical vapour deposition (CVD) onto various transition metals and on insulators. Growth on Ni results in graphitized polycrystalline films. While the thickness of these films can be optimized by controlling the deposition parameters, such as the type of hydrocarbon precursor and temperature, it is difficult to attain single layer graphene (SLG) across large areas, owing to the simultaneous nucleation/growth and solution/precipitation mechanisms. The differing characteristics of polycrystalline Ni films facilitate the growth of graphitic layers at different rates, resulting in regions with differing numbers of graphitic layers. High-quality films can be grown on Cu. Cu is available in a variety of shapes and forms, such as foils, bulks, foams, thin films on other materials and powders, making it attractive for industrial production of large area graphene films. The push to use CVD graphene in applications has also triggered a research line for the direct growth on insulators. The quality of the resulting films is lower than possible to date on metals, but enough, in terms of transmittance and resistivity, for many applications as described in section V. Transfer technologies are the focus of section VI. CVD synthesis of graphene on metals and bottom up molecular approaches require SLG to be transferred to the final target substrates. To have technological impact, the advances in production of high-quality large-area CVD graphene must be commensurate with those on transfer and placement on the final substrates. This is a prerequisite for most applications, such as touch panels, anticorrosion coatings, transparent electrodes and gas sensors etc. New strategies have improved the transferred graphene quality, making CVD graphene a feasible option for CMOS foundries. Methods based on complete etching of the metal substrate in suitable etchants, typically iron chloride, ammonium persulfate, or hydrogen chloride although reliable, are time- and resource-consuming, with damage to graphene and production of metal and etchant residues. Electrochemical delamination in a low-concentration aqueous solution is an alternative. In this case metallic substrates can be reused. Dry transfer is less detrimental for the SLG quality, enabling a deterministic transfer. There is a large range of layered materials (LMs) beyond graphite. Only few of them have been already exfoliated and fully characterized. Section VII deals with the growth of some of these materials. Amongst them, h-BN, transition metal tri- and di-chalcogenides are of paramount importance. The growth of h-BN is at present considered essential for the development of graphene in (opto) electronic applications, as h-BN is ideal as capping layer or substrate. The interesting optical and electronic properties of TMDs also require the development of scalable methods for their production. Large scale growth using chemical/physical vapour deposition or thermal assisted conversion has been thus far limited to a small set, such as h-BN or some TMDs. Heterostructures could also be directly grown. Section VIII discusses advances in GRM functionalization. A broad range of organic molecules can be anchored to the sp(2) basal plane by reductive functionalization. Negatively charged graphene can be prepared in liquid phase (e.g. via intercalation chemistry or electrochemically) and can react with electrophiles. This can be achieved both in dispersion or on substrate. The functional groups of GO can be further derivatized. Graphene can also be noncovalently functionalized, in particular with polycyclic aromatic hydrocarbons that assemble on the sp(2) carbon network by pi-pi stacking. In the liquid phase, this can enhance the colloidal stability of SLG/FLG. Approaches to achieve noncovalent on-substrate functionalization are also discussed, which can chemically dope graphene. Research efforts to derivatize CNMs are also summarized, as well as novel routes to selectively address defect sites. In dispersion, edges are the most dominant defects and can be covalently modified. This enhances colloidal stability without modifying the graphene basal plane. Basal plane point defects can also be modified, passivated and healed in ultra-high vacuum. The decoration of graphene with metal nanoparticles (NPs) has also received considerable attention, as it allows to exploit synergistic effects between NPs and graphene. Decoration can be either achieved chemically or in the gas phase. All LMs,
|
|
3. |
- Sudireddy, B. R., et al.
(författare)
-
Development of Robust Metal-Supported SOFCs and Stack Components in EU METSAPP Consortium
- 2017
-
Ingår i: Fuel Cells. - : Wiley. - 1615-6846 .- 1615-6854. ; 17:4, s. 508-516
-
Tidskriftsartikel (refereegranskat)abstract
- The potential of MS-SOFCs was demonstrated through the previous EU METSOFC project, which concluded that the development of oxidation resistant novel metal-supported solid oxide fule cell (MS-SOFC) design and stack is the requirement to advance this technology to the next level. The following EU METSAPP project has been executed with an overall aim of developing advanced metal-supported cells and stacks based on a robust, reliable and up-scalable technology. During the project, oxidation resistant nanostructured anodes based on modified SrTiO3 were developed and integrated into MS-SOFCs to enhance their robustness. In addition, the manufacturing of metal-supported cells with different geometries, scalability of the manufacturing process was demonstrated and more than 200 cells with an area of approximate to 150 cm(2) were produced. The electrochemical performance of different cell generations was evaluated and best performance and stability combination was observed with doped SrTiO3 based anode designs. Furthermore, numerical models to understand the corrosion behavior of the MS-SOFCs were developed and validated. Finally, the cost effective concept of coated metal interconnects was developed, which resulted in 90% reduction in Cr evaporation, three times lower Cr2O3 scale thickness and increased lifetime. The possibility of assembling these cells into two radically different stack designs was demonstrated.
|
|
4. |
- Bexell, Ulf, et al.
(författare)
-
Bonding of vegetable oils to mercapto silane treated metal surfaces : Surface engineering on the nano scale
- 2006
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:2, s. 838-841
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper the bonding of thin vegetable oil films on mercapto silane treated aluminium surfaces has been studied. The silane molecules are attached to the surface by metal-oxygen-silicon bonds. The coupling between the unsaturated bonds of the vegetable oil and the thiol functionalised surface was obtained through a photoinduced thiol-ene reaction. The surfaces were characterised by X-ray photoelectron spectroscopy (XPS). Vegetable oil contains both saturated and unsaturated carbon chains. For the reactions investigated in this study it is the unsaturated carbon chains that can react by a thiol-ene reaction and the results indicate that it is possible to attach a vegetable oil to a metal surface pre-treated with a thiol functionalised silane.
|
|
5. |
- Ardo, Shane, et al.
(författare)
-
Pathways to electrochemical solar-hydrogen technologies
- 2018
-
Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 11:10, s. 2768-2783
-
Forskningsöversikt (refereegranskat)abstract
- Solar-powered electrochemical production of hydrogen through water electrolysis is an active and important research endeavor. However, technologies and roadmaps for implementation of this process do not exist. In this perspective paper, we describe potential pathways for solar-hydrogen technologies into the marketplace in the form of photoelectrochemical or photovoltaic-driven electrolysis devices and systems. We detail technical approaches for device and system architectures, economic drivers, societal perceptions, political impacts, technological challenges, and research opportunities. Implementation scenarios are broken down into short-term and long-term markets, and a specific technology roadmap is defined. In the short term, the only plausible economical option will be photovoltaic-driven electrolysis systems for niche applications. In the long term, electrochemical solar-hydrogen technologies could be deployed more broadly in energy markets but will require advances in the technology, significant cost reductions, and/ or policy changes. Ultimately, a transition to a society that significantly relies on solar-hydrogen technologies will benefit from continued creativity and influence from the scientific community.
|
|
6. |
- Barros, Djonathan, et al.
(författare)
-
Editing Support for Software Languages: Implementation Practices in Language Server Protocols (Summary)
- 2023
-
Ingår i: Lecture Notes in Informatics. - 1617-5468. ; P-332, s. 35-36
-
Konferensbidrag (refereegranskat)abstract
- We present our paper published at the 25th International Conference on Model Driven Engineering Languages and Systems (MODELS) [Ba22a]. Effectively using software languages requires effective editing support. Modern IDEs, modeling tools, and code editors typically provide sophisticated support to create, comprehend, or modify instancesof particular languages. Unfortunately, building such editing support is challenging. While the engineering of languages is well understood and supported by modern model-driven techniques, there is a lack of engineering principles and best practices for realizing their editing support. We study practices for implementing editing support in so-called language servers-implementations of the language server protocol (LSP). LSP is a recent de facto standard to realize editing support for languages, separated from the editing tools, enhancing the reusability and quality of the editing support. Witnessing the LSP's popularity, we take this opportunity to analyze the implementations of 30 language servers. We identify concerns that developers need to take into account when developing editing support, and we synthesize implementation practices to address them, based on a systematic analysis of the servers' source code. We hope that our results shed light on an important technology for software language engineering, that facilitates language-oriented programming and systems development, including model-driven engineering.
|
|
7. |
|
|
8. |
|
|
9. |
- Lanza, Nina L., et al.
(författare)
-
Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars
- 2016
-
Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 43:14, s. 7398-7407
-
Tidskriftsartikel (refereegranskat)abstract
- The Curiosity rover observed high Mn abundances (>25wt % MnO) in fracture-filling materials that crosscut sandstones in the Kimberley region of Gale crater, Mars. The correlation between Mn and trace metal abundances plus the lack of correlation between Mn and elements such as S, Cl, and C, reveals that these deposits are Mn oxides rather than evaporites or other salts. On Earth, environments that concentrate Mn and deposit Mn minerals require water and highly oxidizing conditions; hence, these findings suggest that similar processes occurred on Mars. Based on the strong association between Mn-oxide deposition and evolving atmospheric dioxygen levels on Earth, the presence of these Mn phases on Mars suggests that there was more abundant molecular oxygen within the atmosphere and some groundwaters of ancient Mars than in the present day
|
|
10. |
- Queiroz, R., et al.
(författare)
-
GeoScenario: An Open DSL for Autonomous Driving Scenario Representation
- 2019
-
Ingår i: IEEE Intelligent Vehicles Symposium 2019. 9-12 June 2019, Paris, France.. - : IEEE. - 9781728105604
-
Konferensbidrag (refereegranskat)abstract
- Automated Driving Systems (ADS) require extensive evaluation to assure acceptable levels of safety before they can operate in real-world traffic. Although many tools are available to perform such tests in simulation, the lack of a language to formally capture test scenarios that cover the complexity of road traffic situations hinders the reproducibility of tests and impairs the exchangeability between tools. We propose GeoScenario as a Domain-Specific Language (DSL) for scenario representation to substantiate test cases in simulation. By adopting GeoScenario in the simulation infrastructure of a self-driving car project, we use the language in practice to test an autonomy stack in simulation. The language was built on top of the well-known Open Street Map standard, and designed to he simple and extensible.
|
|