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- Fomalont, E. B., et al.
(author)
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THE 2014 ALMA LONG BASELINE CAMPAIGN: AN OVERVIEW
- 2015
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In: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 808:1
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Journal article (peer-reviewed)abstract
- A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to similar to 15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from 2014 September to late November, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C 138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at similar to 350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy.
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| 2. |
- Ventura, Alejandra M., et al.
(author)
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Recycled carbon fibers as an alternative reinforcement in UHMWPE composite. Circular economy within polymer tribology
- 2022
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In: Sustainable Materials and Technologies. - : Elsevier. - 2214-9937. ; 34
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Journal article (peer-reviewed)abstract
- The increasing demand of carbon fiber reinforced polymers over the last few decades has brought attention to critical aspects such as disposal, environmental impact, and cost of production. Therefore, adopting a circular economy approach focused on improving efficiency is an enticing alternative nowadays. This investigation is focused on the mechanical and tribological characterization of ultra high molecular weight polyethylene (UHMWPE) composites reinforced with virgin (vCF) and recycled carbon fibers (rCF) under water lubricated conditions. An improvement of 208% in Young's modulus, 105% in ultimate tensile strength and 146% in hardness for the samples with 30%wt rCF, compared to pure UHMWPE, was observed. Reductions of up to 62% in coefficient of friction and 32% in wear rates for 10 wt% CF composites were obtained, facilitated through the formation of a transfer film, which was present on the countersurfaces. The results of this project show that the composites containing recycled fibers exhibit a comparable performance to their virgin counterparts. An economical evaluation estimated possible monetary savings of 910.2 M€ in a time span from 2022 to 2026 by using rCF in composite production, providing arguments for the use of rCF reducing the environmental impact and cost without compromising performance.
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| 3. |
- Kneissl, Lucas M., et al.
(author)
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Mechanical properties and tribological performance of polyoxymethylene/short cellulose fiber composites
- 2023
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In: Polymer testing. - : Elsevier Ltd. - 0142-9418 .- 1873-2348. ; 128
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Journal article (peer-reviewed)abstract
- Natural fibers are promising bio-based materials to use as reinforcements in polymer composites as often more affordable and accessible alternatives to fossil-based fibers, especially because of their superior sustainability. Polyoxymethylene (POM) is a widely used engineering thermoplastic, which has a melting temperature suitable for processing with natural fibers. In this study, such composites consisting of POM and regenerated cellulose fibers have been developed and studied in terms of their mechanical, thermal, tribological and structural properties. Tensile and flexural moduli increased with incorporation of 30 wt% fibers up to 89% and 79% respectively, crystallinity increased as well by a maximum of approx. 11% at 30% fiber content. Furthermore, the specific wear rate was improved for the composite with 10 wt% fibers, showing a decrease of roughly 80%. This study investigates the processing parameters and tribo-mechanical performance of POM-based natural fiber composites as an important route towards future sustainable polymer composites in load bearing applications.
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