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Hendecagram
In geometry, a hendecagram (also endecagram or endekagram) is a star polygon that has eleven vertices. The name ''hendecagram'' combines a Greek numeral prefix, '' hendeca-'', with the Greek suffix ''-gram''. The ''hendeca-'' prefix derives from Greek ἕνδεκα (ἕν + δέκα, one + ten) meaning " eleven". The ''-gram'' suffix derives from γραμμῆς (''grammēs'') meaning a line. Regular hendecagrams There are four regular hendecagrams, which can be described by the notation , , , and ; in this notation, the number after the slash indicates the number of steps between pairs of points that are connected by edges. These same four forms can also be considered as stellations of a regular hendecagon. Since 11 is prime, all hendecagrams are star polygons and not compound figures. Construction As with all odd regular polygons and star polygons whose orders are not products of distinct Fermat primes, the regular hendecagrams cannot be constructed with compass and stra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Star Polygon
In geometry, a star polygon is a type of non- convex polygon. Regular star polygons have been studied in depth; while star polygons in general appear not to have been formally defined, certain notable ones can arise through truncation operations on regular simple and star polygons. Branko Grünbaum identified two primary definitions used by Johannes Kepler, one being the regular star polygons with intersecting edges that don't generate new vertices, and the second being simple isotoxal concave polygons. The first usage is included in polygrams which includes polygons like the pentagram but also compound figures like the hexagram. One definition of a ''star polygon'', used in turtle graphics, is a polygon having 2 or more turns ( turning number and density), like in spirolaterals.Abelson, Harold, diSessa, Andera, 1980, ''Turtle Geometry'', MIT Press, p.24 Etymology Star polygon names combine a numeral prefix, such as ''penta-'', with the Greek suffix '' -gram'' (i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Shuttle Solid Rocket Booster
The Space Shuttle Solid Rocket Booster (SRB) was the first solid-propellant rocket to be used for primary propulsion on a vehicle used for human spaceflight. A pair of these provided 85% of the Space Shuttle's thrust at liftoff and for the first two minutes of ascent. After burnout, they were jettisoned and parachuted into the Atlantic Ocean where they were recovered, examined, refurbished, and reused. The Space Shuttle SRBs were the most powerful solid rocket motors to ever launch humans. The Space Launch System (SLS) SRBs, adapted from the shuttle, surpassed it as the most powerful solid rocket motors ever flown, after the launch of the Artemis-1 mission. Each Space Shuttle SRB provided a maximum thrust, roughly double the most powerful single-combustion chamber liquid-propellant rocket engine ever flown, the Rocketdyne F-1. With a combined mass of about , they comprised over half the mass of the Shuttle stack at liftoff. The motor segments of the SRBs were manufactured by T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hendecagon
In geometry, a hendecagon (also undecagon or endecagon) or 11-gon is an eleven-sided polygon. (The name ''hendecagon'', from Greek ''hendeka'' "eleven" and ''–gon'' "corner", is often preferred to the hybrid ''undecagon'', whose first part is formed from Latin ''undecim'' "eleven".) Regular hendecagon A '' regular hendecagon'' is represented by Schläfli symbol . A regular hendecagon has internal angles of 147. degrees (=147 \tfrac degrees). The area of a regular hendecagon with side length ''a'' is given by. :A = \fraca^2 \cot \frac \simeq 9.36564\,a^2. As 11 is not a Fermat prime, the regular hendecagon is not constructible with compass and straightedge. Because 11 is not a Pierpont prime, construction of a regular hendecagon is still impossible even with the usage of an angle trisector. Close approximations to the regular hendecagon can be constructed. For instance, the ancient Greek mathematicians approximated the side length of a hendecagon inscribed in a unit circl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dihedral Symmetry
In mathematics, a dihedral group is the group of symmetries of a regular polygon, which includes rotations and reflections. Dihedral groups are among the simplest examples of finite groups, and they play an important role in group theory, geometry, and chemistry. The notation for the dihedral group differs in geometry and abstract algebra. In geometry, or refers to the symmetries of the -gon, a group of order . In abstract algebra, refers to this same dihedral group. This article uses the geometric convention, . Definition Elements A regular polygon with n sides has 2n different symmetries: n rotational symmetries and n reflection symmetries. Usually, we take n \ge 3 here. The associated rotations and reflections make up the dihedral group \mathrm_n. If n is odd, each axis of symmetry connects the midpoint of one side to the opposite vertex. If n is even, there are n/2 axes of symmetry connecting the midpoints of opposite sides and n/2 axes of symmetry connecting opp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Barrier
The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first approached the speed of sound, these effects were seen as constituting a barrier, making faster speeds very difficult or impossible. The term ''sound barrier'' is still sometimes used today to refer to aircraft approaching supersonic flight in this high drag regime. Flying faster than sound produces a sonic boom. In dry air at 20 °C (68 °F), the speed of sound is 343 metres per second (about 767 mph, 1234 km/h or 1,125 ft/s). The term came into use during World War II when pilots of high-speed fighter aircraft experienced the effects of compressibility, a number of adverse aerodynamic effects that deterred further acceleration, seemingly impeding flight at speeds close to the speed of sound. These difficulties represented a barrier to flying at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thames & Hudson
Thames & Hudson (sometimes T&H for brevity) is a publisher of illustrated books in all visually creative categories: art, architecture, design, photography, fashion, film, and the performing arts. It also publishes books on archaeology, history, and popular culture. Headquartered in London, it has a sister company in New York City, and subsidiaries in Melbourne, Singapore, and Hong Kong. In Paris it has a sister company, Éditions Thames & Hudson, and a subsidiary called Interart which distributes English-language books. The Thames & Hudson group currently employs approximately 150 staff in London and approximately 65 more around the world. The publishing company was founded in 1949 by Walter and Eva Neurath, who aimed to make the world of art and the research of top scholars available to a wider public. The company's name reflects its international presence, particularly in London and New York. It remains an independent, family-owned company, and is one of the largest publish ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Momine Khatun Mausoleum
Momine Khatun Mausoleum (or Mu'mine Khatun) is a 12th century mausoleum located in the city of Nakchivan in Azerbaijan. The mausoleums of Nakhchivan were nominated for the UNESCO List of World Heritage Sites in 1998 by Gulnara Mehmandarova, the president of the Azerbaijan Committee of ICOMOS. History Momine Khatun Mausoleum, a monument of the Azerbaijani architecture (monuments of the architectural school of Nakhichevan – Maragha) was built in the west part of Nakhchivan city (within the Atabek Complex of Architecture in Nakhchivan city’s historical centre) in 1186. The mausoleum is the only monument that has reached our era from that complex. Shamsaddin Eldaniz, the founder of the Azerbaijan Atabaylar state (Eldiguzids) initiated to erect a mausoleum on the grave of his wife Momine Khatun. However, its construction was finished by Mahammad Jahan Pahlavan, the son of Shamsaddin Eldeniz, in A.H. 582, in the Maharram month (April 1186). According to some investigators, Shams ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Islamic Art
Islamic art is a part of Islamic culture and encompasses the visual arts produced since the 7th century CE by people who lived within territories inhabited or ruled by Muslim populations. Referring to characteristic traditions across a wide range of lands, periods, and genres, Islamic art is a concept used first by Western art historians since the late 19th century. Public Islamic art is traditionally non- representational, except for the widespread use of plant forms, usually in varieties of the spiralling arabesque. These are often combined with Islamic calligraphy, geometric patterns in styles that are typically found in a wide variety of media, from small objects in ceramic or metalwork to large decorative schemes in tiling on the outside and inside of large buildings, including mosques. Other forms of Islamic art include Islamic miniature painting, artefacts like Islamic glass or pottery, and textile arts, such as carpets and embroidery. The early developments of Isla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Girih
''Girih'' ( fa, گره, "knot", also written ''gereh'') are decorative Islamic geometric patterns used in architecture and handicraft objects, consisting of angled lines that form an interlaced strapwork pattern. ''Girih'' decoration is believed to have been inspired by Syrian Roman knotwork patterns from the second century. The earliest ''girih'' dates from around 1000 CE, and the artform flourished until the 15th century. ''Girih'' patterns can be created in a variety of ways, including the traditional straightedge and compass construction; the construction of a grid of polygons; and the use of a set of ''girih'' tiles with lines drawn on them: the lines form the pattern. Patterns may be elaborated by the use of two levels of design, as at the 1453 Darb-e Imam shrine. Square repeating units of known patterns can be copied as templates, and historic pattern books may have been intended for use in this way. The 15th century Topkapı Scroll explicitly shows girih patterns ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Topkapı Scroll
The Topkapı Scroll ( tr, Topkapı Parşömeni) is a Timurid dynasty pattern scroll in the collection of the Topkapı Palace museum. The scroll is a valuable source of information, consisting of 114 patterns that may have been used both indirectly and directly by architects to create the tiling patterns in many mosques around the world, including the quasicrystal Girih tilings from Darb-e Imam. Physical properties The Topkapı scroll is a wide scroll of in length, which is unrolled side to side. One end of the scroll is fixed to a wooden roller, and the other end is glued to a protective leather piece. A number of parchment pieces featuring various patterns are applied on the scroll. The differences in the border of some drawings indicate that the Topkapı Scroll consists of two different scrolls fixed together. The fact that it is not worn out suggests that it was not made to be used as a reference document in a craftman's workshop, but rather than as an exhibition work in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fordham Univ Press
The Fordham University Press is a publishing house, a division of Fordham University, that publishes primarily in the humanities and the social sciences. Fordham University Press was established in 1907 and is headquartered at the university's Lincoln Center campus. It is the oldest Catholic university press in the United States, and the seventh-oldest in the nation. It has been a member of the Association of American University Presses (AAUP) since 1938 and was a founding charter member of the Association of Jesuit University Presses (AJUP). The press was established "not only to represent and uphold the values and traditions of the University itself, but also to further those values and traditions through the dissemination of scholarly research and ideas". History Fordham University Press was established in 1907. After the close of the university's medical school in 1922, the press operated under the Graduate School of Arts and Sciences and began publishing textbooks in educati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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