Da Wikipedia
"The linothorax is a modern term conventionally used to describe a type of upper body armor used by the Ancient Greeks, as well as other civilizations, from the Mycenaean Period through the Hellenistic Period. It is based on the Greek λινοθώραξ (in Homer λινοθώρηξ), which strictly is an adjective meaning "wearing a breastplate of linen" (and is not a noun meaning "linen armor" as often stated); the "linothorax" was made of linen, while a "thorax" was made of metal. The earliest attested account of a "linothorax" used for battle is recorded in Book 2 of Homer's Iliad (2.529 and 2.830). It is worn by Ajax the Lesser and is described in brief. Homer, composing long before the great armies of Athens, Thebes, Sparta or Alexander the Great, surely understood what the armor was. But the extent to which it was used can not be fully determined. An educated guess can be made, however, based on its use by Alexander the Great, and its mention by other sources such as Herodotus (2.182, 3.47, 7.63), Livy (4.19.2–20.7) and Strabo (Geography, 3.3.6, 13.1.10), and many others. The linothorax appears to have been used in place of the bronze 'bell cuirass' as the popular choice of armour for Greek hoplites, starting perhaps around the late seventh century and early sixth century B.C. Its high point, if vase paintings, sculptural reliefs and artistic depictions are to be believed, corresponds with the time of the Persian Wars. By the time of the Peloponnesian War it was still used, and continued to seemingly flourish well into the Hellenistic Period."
Friday, 24 May 2013
After 150 years, the Stirling motor lives
The Sydney Morning Herald, 26 May, 1975
Ford Torino Stirling Special
Ford Torino Stirling Special
da
Modello matematico di motore Stirling accoppiato ad un generatore
elettrico lineare, Michele Favaron
elettrico lineare, Michele Favaron
http://tesi.cab.unipd.it/37661/1/Modello_matematico_di_motore_Stirling_accoppiato_ad_un_generatore_lineare.pdf
Motore di Stirling fatto in casa
Su YouTube cercando "motore stirling fatto in casa" trovate diversi progetti per crearvi il vostro "motore".
A liquid telescope
http://en.wikipedia.org/wiki/Liquid_mirror_telescope
Liquid mirror telescopes are telescopes with mirrors made with a reflective liquid. The most common liquid used is mercury. The container for the liquid is rotating so that the liquid assumes a paraboloidal shape. A paraboloidal shape is precisely the shape needed for the primary mirror of a telescope. The rotating liquid assumes the paraboloidal shape regardless of the container's shape. Liquid mirrors can be a low cost alternative to conventional large telescopes. Compared to a solid glass mirror that must be cast, ground, and polished, a rotating liquid metal mirror is much less expensive to manufacture.
"Isaac Newton noted that the free surface of a rotating liquid forms a circular paraboloid and can therefore be used as a telescope, but he could not actually build one because he had no way to stabilize the speed of rotation[citation needed] (the electric motor did not exist yet). The concept was further developed by Ernesto Capocci of the Naples Observatory (1850), but it was not until 1872 that Henry Skey of Dunedin, New Zealand constructed the first working laboratory liquid mirror telescope."
"Another difficulty is that a telescope with a liquid metal mirror can only be used in zenith telescopes that look straight up at the zenith, so it is not suitable for investigations where the telescope must remain pointing at the same location of space ... Currently, the mercury mirror of the Large Zenith Telescope in Canada is the largest liquid metal mirror in operation. It has a diameter of six meters, and rotates at a rate of about 8.5 revolutions per minute."
Liquid mirror telescopes are telescopes with mirrors made with a reflective liquid. The most common liquid used is mercury. The container for the liquid is rotating so that the liquid assumes a paraboloidal shape. A paraboloidal shape is precisely the shape needed for the primary mirror of a telescope. The rotating liquid assumes the paraboloidal shape regardless of the container's shape. Liquid mirrors can be a low cost alternative to conventional large telescopes. Compared to a solid glass mirror that must be cast, ground, and polished, a rotating liquid metal mirror is much less expensive to manufacture.
"Isaac Newton noted that the free surface of a rotating liquid forms a circular paraboloid and can therefore be used as a telescope, but he could not actually build one because he had no way to stabilize the speed of rotation[citation needed] (the electric motor did not exist yet). The concept was further developed by Ernesto Capocci of the Naples Observatory (1850), but it was not until 1872 that Henry Skey of Dunedin, New Zealand constructed the first working laboratory liquid mirror telescope."
"Another difficulty is that a telescope with a liquid metal mirror can only be used in zenith telescopes that look straight up at the zenith, so it is not suitable for investigations where the telescope must remain pointing at the same location of space ... Currently, the mercury mirror of the Large Zenith Telescope in Canada is the largest liquid metal mirror in operation. It has a diameter of six meters, and rotates at a rate of about 8.5 revolutions per minute."
Variazione entropia
Un esercizio del prof. Mussino che propone un semplice calcolo della variazione d'entropia.
n.5 punto di massa ....
Problema d'esame del Prof. Mussino
Un punto di massa m viene lasciato dalla posizione A con velocità vo= 10 m/s lungo un piano inclinato con angolo θ = 30°; h vale 0.26 m, il coefficiente di attrito dinamico è μ=0.1. Calcolare quanto tempo impiega il punto per arrivare nella posizione B e quanto dovrebbe valere μ per far sì che il punto arrivi in B con velocità nulla.
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