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Homer

Homer is the legendary author of the Iliad and the Odyssey, two epic poems that are the central works of ancient Greek literature. The Iliad is set during the Trojan War, the ten-year siege of the city of Troy by a coalition of Greek kingdoms, it focuses on a quarrel between King Agamemnon and the warrior Achilles lasting a few weeks during the last year of the war. The Odyssey focuses on the ten-year journey home of Odysseus, king of Ithaca, after the fall of Troy. Many accounts of Homer's life circulated in classical antiquity, the most widespread being that he was a blind bard from Ionia, a region of central coastal Anatolia in present-day Turkey. Modern scholars consider these accounts legendary; the Homeric Question – concerning by whom, when and under what circumstances the Iliad and Odyssey were composed – continues to be debated. Broadly speaking, modern scholarly opinion falls into two groups. One holds that most of the Odyssey are the works of a single poet of genius; the other considers the Homeric poems to be the result of a process of working and reworking by many contributors, that "Homer" is best seen as a label for an entire tradition.

It is accepted that the poems were composed at some point around the late eighth or early seventh century BC. The poems are in Homeric Greek known as Epic Greek, a literary language which shows a mixture of features of the Ionic and Aeolic dialects from different centuries. Most researchers believe that the poems were transmitted orally. From antiquity until the present day, the influence of Homeric epic on Western civilization has been great, inspiring many of its most famous works of literature, music and film; the Homeric epics were the greatest influence on education. Today only the Iliad and Odyssey are associated with the name'Homer'. In antiquity, a large number of other works were sometimes attributed to him, including the Homeric Hymns, the Contest of Homer and Hesiod, the Little Iliad, the Nostoi, the Thebaid, the Cypria, the Epigoni, the comic mini-epic Batrachomyomachia, the Margites, the Capture of Oechalia, the Phocais; these claims are not considered authentic today and were by no means universally accepted in the ancient world.

As with the multitude of legends surrounding Homer's life, they indicate little more than the centrality of Homer to ancient Greek culture. Many traditions circulated in the ancient world concerning Homer. Modern scholarly consensus is; some claims were repeated often. They include that Homer was blind, that he was born in Chios, that he was the son of the river Meles and the nymph Critheïs, that he was a wandering bard, that he composed a varying list of other works, that he died either in Ios or after failing to solve a riddle set by fishermen, various explanations for the name "Homer"; the two best known ancient biographies of Homer are the Life of Homer by the Pseudo-Herodotus and the Contest of Homer and Hesiod. The study of Homer is one of the oldest topics in scholarship, dating back to antiquity. Nonetheless, the aims of Homeric studies have changed over the course of the millennia; the earliest preserved comments on Homer concern his treatment of the gods, which hostile critics such as the poet Xenophanes of Colophon denounced as immoral.

The allegorist Theagenes of Rhegium is said to have defended Homer by arguing that the Homeric poems are allegories. The Iliad and the Odyssey were used as school texts in ancient Greek and Hellenistic cultures, they were the first literary works taught to all students. The Iliad its first few books, was far more intently studied than the Odyssey during the Hellenistic and Roman periods; as a result of the poems' prominence in classical Greek education, extensive commentaries on them developed to explain parts of the poems that were culturally or linguistically difficult. During the Hellenistic and Roman periods, many interpreters the Stoics, who believed that Homeric poems conveyed Stoic doctrines, regarded them as allegories, containing hidden wisdom; because of the Homeric poems' extensive use in education, many authors believed that Homer's original purpose had been to educate. Homer's wisdom became so praised that he began to acquire the image of a prototypical philosopher. Byzantine scholars such as Eustathius of Thessalonica and John Tzetzes produced commentaries and scholia to Homer in the twelfth century.

Eustathius's commentary on the Iliad alone is massive, sprawling over nearly 4,000 oversized pages in a twenty-first century printed version and his commentary on the Odyssey an additional nearly 2,000. In 1488, the Greek scholar Demetrios Chalkokondyles published the editio princeps of the Homeric poems; the earliest modern Homeric scholars started with the same basic approaches towards the Homeric poems as scholars in antiquity. The allegorical interpretation of the Homeric poems, so prevalent in antiquity returned to become the prevailing view of the Renaissance. Renaissance humanists praised Homer as the archetypically wise poet, whose writings contain hidden wisdom, disguised through allegory. In western Europe during the Renaissance, Virgil was more read than Homer and Homer was seen through a Virgilian lens. In 1664, contradicting the widespread praise of Homer as the epitome of wisdom, François Hédelin, abbé d'Aubignac wrote a s

Martensite

Martensite is a hard form of steel crystalline structure. It is named after the German metallurgist Adolf Martens. By analogy the term can refer to any crystal structure, formed by diffusionless transformation. Martensite is formed in carbon steels by the rapid cooling of the austenite form of iron at such a high rate that carbon atoms do not have time to diffuse out of the crystal structure in large enough quantities to form cementite. Austenite is γ-Fe, a solid solution of iron and alloying elements; as a result of the quenching, the face-centered cubic austenite transforms to a strained body-centered tetragonal form called martensite, supersaturated with carbon. The shear deformations that result produce a large number of dislocations, a primary strengthening mechanism of steels; the highest hardness of a pearlitic steel is 400 Brinell. The martensitic reaction begins during cooling when the austenite reaches the martensite start temperature and the parent austenite becomes mechanically unstable.

As the sample is quenched, an large percentage of the austenite transforms to martensite until the lower transformation temperature Mf is reached, at which time the transformation is completed. For a eutectoid steel, between 6 and 10% of austenite, called retained austenite, will remain; the percentage of retained austenite increases from insignificant for less than 0.6% C steel, to 13% retained austenite at 0.95% C and 30–47% retained austenite for a 1.4% carbon steels. A rapid quench is essential to create martensite. For a eutectoid carbon steel of thin section, if the quench starting at 750 °C and ending at 450 °C takes place in 0.7 seconds no pearlite will form and the steel will be martensitic with small amounts of retained austenite. For steel 0-0.6% carbon the martensite has the appearance of lath, is called lath martensite. For steel greater than 1 % carbon. Between those two percentages, the physical appearance of the grains is a mix of the two; the strength of the martensite is reduced.

If the cooling rate is slower than the critical cooling rate, some amount of pearlite will form, starting at the grain boundaries where it will grow into the grains until the Ms temperature is reached the remaining austenite transforms into martensite at about half the speed of sound in steel. In certain alloy steels, martensite can be formed by the working and hence deformation of the steel at temperature, while it is in its austenitic form, by quenching to below Ms and working by plastic deformations to reductions of cross section area between 20% to 40% of the original; the process produces dislocation densities up to 1013/cm2. The great number of dislocations, combined with precipitates that originate and pin the dislocations in place, produces a hard steel; this property is used in toughened ceramics like yttria-stabilized zirconia and in special steels like TRIP steels. Thus, martensite can be stress induced. One of the differences between the two phases is that martensite has a body-centered tetragonal crystal structure, whereas austenite has a face-centered cubic structure.

The growth of martensite phase requires little thermal activation energy because the process is a diffusionless transformation, which results in the subtle but rapid rearrangement of atomic positions, has been known to occur at cryogenic temperatures. Martensite has a lower density than austenite, so that the martensitic transformation results in a relative change of volume. Of greater importance than the volume change is the shear strain, which has a magnitude of about 0.26 and which determines the shape of the plates of martensite. Martensite is not shown in the equilibrium phase diagram of the iron-carbon system because it is not an equilibrium phase. Equilibrium phases form by slow cooling rates that allow sufficient time for diffusion, whereas martensite is formed by high cooling rates. Since chemical processes accelerate at higher temperature, martensite is destroyed by the application of heat; this process is called tempering. In some alloys, the effect is reduced by adding elements such as tungsten that interfere with cementite nucleation, more than not, the nucleation is allowed to proceed to relieve stresses.

Since quenching can be difficult to control, many steels are quenched to produce an overabundance of martensite tempered to reduce its concentration until the preferred structure for the intended application is achieved. The needle-like microstructure of martensite leads to brittle behavior of the material. Too much martensite leaves steel brittle. Eutectic Eutectoid Ferrite Maraging steel Spring steel Tool steel Comprehensive resources on martensite, from the University of Cambridge Metallurgy for the Non-Metallurgist from the American Society for Metals PTCLab---Capable of calculating martensite crystallography with single shear or double shear theory

The Letters of J. R. R. Tolkien

The Letters of J. R. R. Tolkien is a selection of J. R. R. Tolkien's letters published in 1981, edited by Tolkien's biographer Humphrey Carpenter assisted by Christopher Tolkien; the selection contains 354 letters, dating between October 1914, when Tolkien was an undergraduate at Oxford, 29 August 1973, four days before his death. The letters can be divided in four categories: Personal letters to Tolkien's wife Edith, to his son Christopher Tolkien and his other children, Letters about Tolkien's career as a professor of Anglo-Saxon Letters to his publishers at Allen & Unwin explaining his failing to meet the deadline and related topics Letters about Middle-earthThe last category is of interest to Tolkien fans, as it provides a lot of information about Middle-earth which cannot be found anywhere in the works published by Tolkien himself. In letters 29 and 30, it appears that a German translation of The Hobbit was being negotiated in 1938; the German firm enquired. Tolkien was infuriated by this, wrote two drafts of possible replies for his publisher to choose.

The first one is not present – in it Tolkien is assumed to have refused to give any declaration whatsoever of his racial origins. The second, draft included: Thank you for your letter... I regret. I am not of Aryan extraction:, Indo-Iranian, but if I am to understand that you are enquiring whether I am of Jewish origin, I can only reply that I regret that I appear to have no ancestors of that gifted people. A former signals officer at the Battle of the Somme, Tolkien expressed his great dislike for war, whatever the cause; this is evident in a great many letters which he wrote during the Second World War to his son Christopher, which invoke a sense of gloom. Notable among these is his reaction to the atomic bombing of Hiroshima, in which he refers to the bombmakers of the Manhattan Project as "lunatics" and "Babel builders". Tolkien Letters FAQ at the Wayback Machine The Letters of J. R. R. Tolkien on Tolkien Library The Letters of J. R. R. Tolkien video