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Brocot Table
Louis Achille Brocot (pronounced "broco") (11 July 1817 – 19 January 1878) was a French clockmaker. and amateur mathematician.. He is known for his discovery (contemporaneously with, but independently of, German number theorist Moritz Stern) of the Stern–Brocot tree, a mathematical structure useful in approximating real numbers by rational numbers; this sort of approximation is an important part of the design of gear ratios for clocks. Several improvements in clock design were attributed to Brocot. He invented the "Brocot Suspension", which enabled time keeping to be regulated by altering the length of the pendulum suspension spring by a key turned in the dia He also made many practical horological innovations including refinement of his father Louis-Gabriel's pin-pallet escapement, Brocot escapement and the development of clocks with perpetual calendar mechanisms.. In order to commercially exploit his original designs, together with Jean-Baptiste Delettrez (Antoine) Je ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
French People
The French people (french: Français) are an ethnic group and nation primarily located in Western Europe that share a common French culture, history, and language, identified with the country of France. The French people, especially the native speakers of langues d'oïl from northern and central France, are primarily the descendants of Gauls (including the Belgae) and Romans (or Gallo-Romans, western European Celtic and Italic peoples), as well as Germanic peoples such as the Franks, the Visigoths, the Suebi and the Burgundians who settled in Gaul from east of the Rhine after the fall of the Roman Empire, as well as various later waves of lower-level irregular migration that have continued to the present day. The Norse also settled in Normandy in the 10th century and contributed significantly to the ancestry of the Normans. Furthermore, regional ethnic minorities also exist within France that have distinct lineages, languages and cultures such as Bretons in Brittany, Occi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clockmaker
A clockmaker is an artisan who makes and/or repairs clocks. Since almost all clocks are now factory-made, most modern clockmakers only repair clocks. Modern clockmakers may be employed by jewellers, antique shops, and places devoted strictly to repairing clocks and watches. Clockmakers must be able to read blueprints and instructions for numerous types of clocks and time pieces that vary from antique clocks to modern time pieces in order to fix and make clocks or watches. The trade requires fine motor coordination as clockmakers must frequently work on devices with small gears and fine machinery. Originally, clockmaker were master craftsmen who designed and built clocks by hand. Since modern clockmakers are required to repair antique, handmade or one-of-a-kind clocks for which parts are not available, they must have some of the design and fabrication abilities of the original craftsmen. A qualified clockmaker can typically design and make a missing piece for a clock without a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moritz Stern
Moritz Abraham Stern (29 June 1807 – 30 January 1894) was a German mathematician. Stern became ''Ordinarius'' (full professor) at Göttingen University in 1858, succeeding Carl Friedrich Gauss. Stern was the first Jewish full professor at a German university who attained the position without changing his Jewish religion. Although Carl Gustav Jacobi preceded him (by three decades) as the first Jew to obtain a math professorial chair in Germany, Jacobi's family had converted to Christianity long before then. As a professor, Stern taught Gauss's student Bernhard Riemann. Stern was very helpful to Gotthold Eisenstein in formulating a proof of the quadratic reciprocity theorem. Stern was interested in primes that cannot be expressed as the sum of a prime and twice a square (now known as Stern primes). He is known for formulating Stern's diatomic series Stern's (originally Stern Brothers) was a regional department store chain serving the U.S. states of New York, New Jersey, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Real Number
In mathematics, a real number is a number that can be used to measure a ''continuous'' one-dimensional quantity such as a distance, duration or temperature. Here, ''continuous'' means that values can have arbitrarily small variations. Every real number can be almost uniquely represented by an infinite decimal expansion. The real numbers are fundamental in calculus (and more generally in all mathematics), in particular by their role in the classical definitions of limits, continuity and derivatives. The set of real numbers is denoted or \mathbb and is sometimes called "the reals". The adjective ''real'' in this context was introduced in the 17th century by René Descartes to distinguish real numbers, associated with physical reality, from imaginary numbers (such as the square roots of ), which seemed like a theoretical contrivance unrelated to physical reality. The real numbers include the rational numbers, such as the integer and the fraction . The rest of the real number ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rational Number
In mathematics, a rational number is a number that can be expressed as the quotient or fraction of two integers, a numerator and a non-zero denominator . For example, is a rational number, as is every integer (e.g. ). The set of all rational numbers, also referred to as "the rationals", the field of rationals or the field of rational numbers is usually denoted by boldface , or blackboard bold \mathbb. A rational number is a real number. The real numbers that are rational are those whose decimal expansion either terminates after a finite number of digits (example: ), or eventually begins to repeat the same finite sequence of digits over and over (example: ). This statement is true not only in base 10, but also in every other integer base, such as the binary and hexadecimal ones (see ). A real number that is not rational is called irrational. Irrational numbers include , , , and . Since the set of rational numbers is countable, and the set of real numbers is uncountable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gear Ratio
A gear train is a mechanical system formed by mounting gears on a frame so the teeth of the gears engage. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission of rotation from one gear to the next. Features of gears and gear trains include: * The gear ratio of the pitch circles of mating gears defines the speed ratio and the mechanical advantage of the gear set. * A planetary gear train provides high gear reduction in a compact package. * It is possible to design gear teeth for gears that are non-circular, yet still transmit torque smoothly. * The speed ratios of chain and belt drives are computed in the same way as gear ratios. See bicycle gearing. The transmission of rotation between contacting toothed wheels can be traced back to the Antikythera mechanism of Greece and the south-pointing chariot of China. Illustrations by the Renaissance scientist Georgius Agricola show gear trains with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pin-pallet Escapement
A Roskopf, pin-lever, or pin-pallet escapement is an inexpensive, less accurate version of the lever escapement, used in mechanical alarm clocks, kitchen timers, mantel clocks and, until the 1970s, cheap watches now known as pin lever watches. It was popularized by German watchmaker Georges Frederic Roskopf in it "proletarian watch" from 1867. It was invented by Louis Perron, of Besançon, suggested to Roskopf by Jules Grossmann. Background An escapement is the mechanism in a mechanical timepiece that gives the balance wheel pushes to keep it moving back and forth, and releases the timepiece's gears to advance a fixed amount with each swing of the wheel, thus moving the hands forward at a steady rate. The pin pallet escapement is similar to the lever escapement, which is used in quality watches, except that the horizontal jewel pallets on the lever are replaced with vertical metal pins, and the shape of the escape wheel teeth is modified. The pin pallet escapement was widely ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perpetual Calendar
A perpetual calendar is a calendar valid for many years, usually designed to look up the day of the week for a given date in the past or future. For the Gregorian and Julian calendars, a perpetual calendar typically consists of one of three general variations: # 14 one-year calendars, plus a table to show which one-year calendar is to be used for any given year. These one-year calendars divide evenly into two sets of seven calendars: seven for each common year (the year that does not have a February 29) with each of the seven starting on a different day of the week, and seven for each leap year, again with each one starting on a different day of the week, totaling fourteen. (See Dominical letter for one common naming scheme for the 14 calendars.) # Seven (31-day) one-month calendars (or seven each of 28–31 day month lengths, for a total of 28) and one or more tables to show which calendar is used for any given month. Some perpetual calendars' tables slide against each othe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jean-Baptiste Delettrez
(Antoine) Jean-Baptiste Delettrez (1 May 1816 – 25 May 1887) was a renowned 19th-century French clockmaker. Delettrez and Achille Brocot, son of the respected clockmaker Louis-Gabriel Brocot, established the clockmaking company "Brocot et Delettrez" in Paris on 20 October 1851, with premises at 62 Rue Charlot. Delettrez worked alongside Achille Brocot for several years and their clock movements are considered to be the most effective made during the late 19th centuryTheir speciality was a range of clocks based on the innovations of Brocot père and his other son Antoine, but generally of Achille's greatly advanced original design, some having a unique single-arm double-wheel escapement, some having a temperature-compensated pendulum, some having two dials, one of which showed the time and the other which showed a calendar and often other information such as phases of the moon, times of sunrise & sunset in Paris, etc. The firm was awarded a 1st class prize at the Paris World Ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1817 Births
Events January–March * January 1 – Sailing through the Sandwich Islands, Otto von Kotzebue discovers New Year Island. * January 19 – An army of 5,423 soldiers, led by General José de San Martín, starts crossing the Andes from Argentina, to liberate Chile and then Peru. * January 20 – Ram Mohan Roy and David Hare found Hindu College, Calcutta, offering instructions in Western languages and subjects. * February 12 – Battle of Chacabuco: The Argentine–Chilean patriotic army defeats the Spanish. * March 3 ** President James Madison vetoes John C. Calhoun's Bonus Bill. ** The U.S. Congress passes a law to split the Mississippi Territory, after Mississippi drafts a constitution, creating the Alabama Territory, effective in August. * March 4 – James Monroe is sworn in as the fifth President of the United States. * March 21 – The flag of the Pernambucan Revolt is publicly blessed by the dean of Recife Cathedral, Brazil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1878 Deaths
Events January–March * January 5 – Russo-Turkish War – Battle of Shipka Pass IV: Russian and Bulgarian forces defeat the Ottoman Empire. * January 9 – Umberto I becomes King of Italy. * January 17 – Battle of Philippopolis: Russian troops defeat the Turks. * January 23 – Benjamin Disraeli orders the British fleet to the Dardanelles. * January 24 – Russian revolutionary Vera Zasulich shoots at Fyodor Trepov, Governor of Saint Petersburg. * January 28 – ''The Yale News'' becomes the first daily college newspaper in the United States. * January 31 – Turkey agrees to an armistice at Adrianople. * February 2 – Greece declares war on the Ottoman Empire. * February 7 – Pope Pius IX dies, after a 31½ year reign (the longest definitely confirmed). * February 8 – The British fleet enters Turkish waters, and anchors off Istanbul; Russia threatens to occupy Istanbul, but does not carry out the threat. * Feb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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