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AlMangour B (2019) Additive manufacturing of emerging materials. Springer Nature, Cham, Switzerland. Following that statement, Bernard knows that May and June are ruled out. Then, Bernard is able to know which month it is. So it must be either July 16, August 15, or August 17 (not the 14th as then he can't know for sure whether it's July or August). Since Albert subsequently can also be sure of the date, he must know it's July. If it's August, he can't be sure as it could be August 15 or 17." Nuechterlein J, Iten J (2016) Reactive additive manufacturing. Patent Application Publication No. US2016/0271878A1 Sep.22,2016
Active remote sensing systems emit radiation toward the target using their own energy source and detect radiation reflected from that target. An important advantage for active sensors is their ability to obtain measurements independently of sun illumination conditions and largely independent of weather conditions [ 3]. The chosen AM technology is the SLM. It belongs to the category of the powder bed fusion [ 20]. The process uses the thermal energy provided by a laser source to selectively melts regions of a powder bed. This way it is possible to fabricate layer by layer full dense metallic components characterized by very complex geometries and good mechanical properties [ 21, 22]. Heidler N Hilpert E, Hartung J, Albert T (2017) Lightweight structures for metal mirrors. EUSPEN Dimensional Accuracy and Surface Finish in Additive Manufacturing, KU Leuven, BE Boschetto A, Bottini L, Veniali F (2017) Roughness modeling of AlSi10Mg parts fabricated by selective laser melting. J Mater Process Technol 241:154–163. https://doi.org/10.1016/j.jmatprotec.2016.11.013Field doesn’t want to carpet the Arctic in glass. Instead, she plans on distributing it strategically to protect some particularly fast-melting, vulnerable areas, like the Fram Strait, a thin passage between Greenland and Svalbard. According to results of a climate model she presented last December at the annual meeting of the American Geophysical Union, treating the Fram Strait could lead to large-scale ice regrowth across parts of the Arctic. Terry ground the mirror against the convex disc using ever finer pastes of water mixed with sand, from coarse, gritty grades right down to ground pumice stone as smooth as flour. He then polished it to a high shine on a bed of slightly softened set pitch, or tar, with polishing powder. This is exactly what earlier astronomers did: William Herschel ground his speculum metal mirrors with coarse emery and water; Newton polished his on a bed of pitch while John Hadley similarly used pitch-soaked silk. Left: The coarsest sand used for grinding the mirror. Sand sold in pet shops to line birdcages proved particularly effective! Right: The bed of pitch, also known as the pitch-lap or polishing-lap, on which the mirror was finally polished. Credit: Matthew Howles.
In the question, you're given 10 dates across four months - May 15, 16, and 19, June 17 and 19, July 14 and 16, and August 14, 15, and 17. Then, you're given a couple of cryptic quotes from Albert, who only knows the month Cheryl was born, and Bernard, who only knows the date. Artists Necole Schmitz, Stephen Coles and Katie Surridge took on the casting processes, melting the specially alloyed speculum metal in a chimney furnace at over 1000 degrees Celsius before pouring it into disc-shaped moulds. There has been some discussion about whether infection changes human behaviour or not, possibly making some infected humans more likely to take risks, but it's certainly not a dramatic behavioural change like we see with zombies. This would result in a much colder climate for the UK while accelerating warmth in the tropics. Some scientists predict this could happen next century. James Gray, Chair of the polar research sub-committee, said: "For too long the effects of a changing Arctic have been out of sight, out of mind. Before melting glaciers and ice sheets contribute to widespread flooding and irreversible weather patterns in the UK, we must throw our full toolbox at understanding changes in the Arctic better." Kovalev VA, Eichinger WE (2004) Elastic Lidar: theory, practice, and analysis methods. Wiley-Interscience
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The motivation of the use of the AM technology is the introduction of internal lattice structures, aiming to reduce the component weight without compromising the performance. To furtherly improve the mechanical properties, an AA2024 MMC is used. Making a historically sympathetic telescope mirror involves two key processes: first, the metal is cast in the shape of a disc; then, the surface of the disc is ground and polished to a smooth, accurate mirror finish. Speculum metal is now virtually obsolete as a material, but thanks to the virtuoso skills and tireless efforts of some truly talented contemporary artists, we were able to meet this somewhat unpredictable challenge head-on. Transformed: our speculum metal mirror before (left) and after (right) polishing. Even though some light pitting remains in the mirror’s surface, this doesn’t affect its optical quality. Credit: Matthew Howles. The work underlines that the AM metal mirror fabrication can have an important progress by combining the geometrical design with new high performance MMC materials. However, the integration with the secondary finishing operation and the deformation induced by the assembly are of primary importance to assure the functionality. Mirrors manufacturing with traditional computer numerical control (CNC) technologies have limitations on mass reduction. Additive manufacturing (AM) methods offer new concepts for production of metal optics that can overcome the specific limitations of CNC technologies. Internal structures can be designed with a variety of configurations, such as periodic structures [ 6], honeycomb cells [ 7, 8] , and topologically optimized structures [ 9, 10, 11]. Zhang K, Qu H, Guan H et al (2021) Design and fabrication technology of metal mirrors based on additive manufacturing: a review. Appl Sci 11(22):10630. https://doi.org/10.3390/app112210630
Bottini L (2021) Study of selective laser melting process parameters to improve the obtainable roughness of AlSi10Mg parts. Selected Topics in Manufacturing. pp 121–139. Springer, Cham. https://doi.org/10.1007/978-3-030-57729-2_9 Xu C, Peng X, Liu J et al (2022) (2022) A high efficiency and precision smoothing polishing method for NiP coating of metal mirror. Micromachines 13:1171. https://doi.org/10.3390/mi13081171 The interferometric measurement pointed out that the fabricated mirror must be finished and measured in the same way as the final assembled configuration; otherwise, it exceeds the required limits, as evidenced in the free arrangement. We must prioritise and put more funding behind scientific and multi-disciplinary research. At the moment, Arctic science is concentrated on its summer, with the Arctic winter which could tell us an enormous amount about the weather being under-studied. More collaboration is needed among UK universities to avoid repetition of scientific endeavours seeking out the same information, and with our international partners to learn and share resource." https://www.elementum3d.com/wp-content/uploads/2021/12/An-inside-look-at-how-AM-commercial-aluminum-alloys-are-made-possible-using-RAM-technology.pdf
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Atkins C, Brzozowski W, Dobson N et al (2019) Lightweighting design optimisation for additively manufactured mirrors. Proceedings Volume 11116, Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems II. https://doi.org/10.1117/12.2528105 Due to climate warming, irreversibly thawing permafrost is releasing organic matter frozen for up to a million years, most of which decomposes into carbon dioxide and methane, further enhancing the greenhouse effect. Liu G, Guo L, Wang X, Wu Q (2018) Topology and parametric optimization based lightweight design of a space reflective mirror. Opt Eng 57(7):1. https://doi.org/10.1117/1.OE.57.7.075101 This measurement principle is usually referred to as time of flight (ToF). ToF can be obtained by sending through a laser a pulsed signal, and by measuring the phase and frequency of the reflected light signal with respect to a reference. The rising sea levels will erode British coasts and put homes at risk, with the Thames barrier needing an upgrade to cope with higher tides. Later in the century, governments will likely have to decide where they will build defences and where they will allow flooding to occur.
It may sound straightforward enough, but grinding and polishing a speculum metal mirror is not for the faint-hearted. Caroline Herschel, sister of William and herself an accomplished astronomer who went on to discover eight comets, wrote of her ‘attendance on my Brother when polishing, that by way of keeping him alife I was even obliged to feed him by putting the Vitals by bits into his mouth – this was once the case when at the finishing of a 7 foot mirror, he had not left his hands from it for 16 hours together’ (Michael Hoskin (ed.), Caroline Herschel’s Autobiographies (Cambridge, 2003) p. 55). The mirror disc’s concave surface then had to be ground against another metal disc with an equally matching convex surface. This grinds out imperfections from the casting process to make the mirror smoother and more reflective and helps to grind a more accurate curve into the mirror.We had a go at making speculum metal telescope mirrors – arsenic NOT included – as part of a “how-it’s-made” film for the Science City gallery. We wanted to showcase some of the extraordinary craft skills needed to produce many of the historical scientific instruments in our collection. The choice was made to use a star trabecular structure which allows excellent quality in the fabrication of the beams, when properly inclined, using SLM technology.
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