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Kiffa Beads
Kiffa beads are rare powder glass beads. They are named after the Mauritanian city of Kiffa, where France, French ethnology, ethnologist R. Mauny documented them first in 1949. Kiffa beads represent one of the highest levels of artistic skill and ingenuity in beadmaking, being manufactured with the simplest materials and tools available: pulverized European glass beads or fragments of them, bottle glass, pottery shards, tin cans, twigs, steel Sewing needle, needles, some gum arabic, and open fires. The term Kiffa bead, named after one of the old bead making centres of Kiffa in Mauritania, was coined by United States bead collectors during the 1980s. According to Peter Francis, Jr., the making of powder glass beads in West Africa may date back a few hundred years, and to possibly 1200 CE in Mauritania. Maure powder glass beads are believed to copy older, Islamic beads, of the type made in Fustat and elsewhere. Although the making of Mauritanian powder glass beads appears to be an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kiffa Bead Cone
Kiffa () is a large town in the far south region of Mauritania, and the name of an administrative area within the local Assaba Region. Kiffa is located at , some from the coast and at the western end of the Aoukar sand sea of southern Mauritania. Climate Kiffa has a hot desert climate (Köppen climate classification ''BWh''). The climate is Sahelian, with April to June as the hottest months and eighty-five percent of the low annual rainfall occurring from July to September. In the 1990s and early 2000s Kiffa benefited from higher rainfall levels than elsewhere in the western Sahel. While Kiffa benefits from the ongoing "greening of the Sahel" the area's rangeland forage ecosystems remain vulnerable and can be subject to damaging overgrazing. Population, infrastructure and agriculture Kiffa was allowed to grow haphazardly and to sprawl during the later 20th century, and it has continued to do so. Near Kiffa is Kiffa Airport which has a tarmac runway of over 1,600 y ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
West Africa
West Africa, also known as Western Africa, is the westernmost region of Africa. The United Nations geoscheme for Africa#Western Africa, United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, and Togo, as well as Saint Helena, Ascension and Tristan da Cunha (United Kingdom Overseas Territories, United Kingdom Overseas Territory).Paul R. Masson, Catherine Anne Pattillo, "Monetary union in West Africa (ECOWAS): is it desirable and how could it be achieved?" (Introduction). International Monetary Fund, 2001. The population of West Africa is estimated at around million people as of , and at 381,981,000 as of 2017, of which 189,672,000 were female and 192,309,000 male.United Nations Department of Economic and Social Affairs, Population Division (2017). World Population Prospects: The 2017 Revision, custom data acquired via webs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Obverse
The obverse and reverse are the two flat faces of coins and some other two-sided objects, including paper money, flags, seals, medals, drawings, old master prints and other works of art, and printed fabrics. In this usage, ''obverse'' means the front face of the object and ''reverse'' means the back face. The obverse of a coin is commonly called ''heads'', because it often depicts the head of a prominent person, and the reverse ''tails''. In numismatics, the abbreviation ''obv.'' is used for ''obverse'',David Sear. ''Greek Imperial Coins and Their Values.'' Spink Books, 1982. p. xxxv. while , )(Jonathan Edwards. ''Catalogue of the Greek and Roman Coins in the Numismatic Collection of Yale College, Volume 2.'' Tuttle, Morehouse & Taylor, 1880. p. 228. and ''rev.''Allen G. Berman. ''Warman's Coins And Paper Money: Identification and Price Guide.'' Penguin, 2008. are used for ''reverse''. Vexillologists use the symbols "normal" for the obverse and "reverse" for the r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oblate Spheroid
A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circular symmetry. If the ellipse is rotated about its major axis, the result is a ''prolate spheroid'', elongated like a rugby ball. The American football is similar but has a pointier end than a spheroid could. If the ellipse is rotated about its minor axis, the result is an ''oblate spheroid'', flattened like a lentil or a plain M&M. If the generating ellipse is a circle, the result is a sphere. Due to the combined effects of gravity and rotation, the figure of the Earth (and of all planets) is not quite a sphere, but instead is slightly flattened in the direction of its axis of rotation. For that reason, in cartography and geodesy the Earth is often approximated by an oblate spheroid, known as the reference ellipsoid, instead of a sphe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polychromatic
Polychrome is the "practice of decorating architectural elements, sculpture, etc., in a variety of colors." The term is used to refer to certain styles of architecture, pottery, or sculpture in multiple colors. When looking at artworks and architecture from Ancient history, antiquity and the European Middle Ages, people tend to believe that they were monochrome. In reality, the pre-Renaissance past was full of colour, and Greco-Roman sculptures and Gothic architecture, Gothic cathedrals, that are now white, beige, or grey, were initially painted in a variety of colours. As André Malraux stated: "Athens was never white but her statues, bereft of color, have conditioned the artistic sensibilities of Europe [...] the whole past has reached us colorless." Polychrome was and is a practice not limited only to the Western world. Non-Western artworks, like Chinese architecture, Chinese temples, Oceanian art, Oceanian Uli figures, or Maya ceramics, Maya ceramic vases, were also decora ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molding (process)
Molding (American English) or moulding ( British and Commonwealth English; see spelling differences) is the process of manufacturing by shaping liquid or pliable raw material using a rigid frame called a mold or matrix. This itself may have been made using a pattern or model of the final object. A mold or mould is a hollowed-out block that is filled with a liquid or pliable material such as plastic, glass, metal, or ceramic raw material. The liquid hardens or sets inside the mold, adopting its shape. A mold is a counterpart to a cast. The very common bi-valve molding process uses two molds, one for each half of the object. Articulated molds have multiple pieces that come together to form the complete mold, and then disassemble to release the finished casting; they are expensive, but necessary when the casting shape has complex overhangs. Piece-molding uses a number of different molds, each creating a section of a complicated object. This is generally only used for larg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steel
Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength and low raw material cost, steel is one of the most commonly manufactured materials in the world. Steel is used in structures (as concrete Rebar, reinforcing rods), in Bridge, bridges, infrastructure, Tool, tools, Ship, ships, Train, trains, Car, cars, Bicycle, bicycles, Machine, machines, Home appliance, electrical appliances, furniture, and Weapon, weapons. Iron is always the main element in steel, but other elements are used to produce various grades of steel demonstrating altered material, mechanical, and microstructural properties. Stainless steels, for example, typically contain 18% chromium and exhibit improved corrosion and Redox, oxidation resistance versus its carbon steel counterpart. Under atmospheric pressures, steels generally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slurry
A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pump. The size of solid particles may vary from 1 micrometre up to hundreds of millimetres. The particles may settle below a certain transport velocity and the mixture can behave like a Newtonian or non-Newtonian fluid. Depending on the mixture, the slurry may be abrasive and/or corrosive. Examples Examples of slurries include: *Cement slurry, a mixture of cement, water, and assorted dry and liquid additives used in the petroleum and other industries *Soil/cement slurry, also called Controlled Low-Strength Material (CLSM), flowable fill, controlled density fill, flowable mortar, plastic soil-cement, K-Krete, and other names *A mixture of thickening agent, oxidizers, and water used to form a gel explosive *A mixture of pyroclastic materi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saliva
Saliva (commonly referred as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be extracted), enzymes (such as lingual lipase and amylase), and antimicrobial agents (such as secretory IgA, and lysozymes). The enzymes found in saliva are essential in beginning the process of digestion of dietary starches and fats. These enzymes also play a role in breaking down food particles entrapped within dental crevices, thus protecting teeth from bacterial decay. Saliva also performs a lubricating function, wetting food and permitting the initiation of swallowing, and protecting the oral mucosa from drying out. Saliva has specialized purposes for a variety of animal species beyond predigestion. Certain swifts construct nests with their sticky saliva. The foundation of bird's nest soup is an aerodramus nest. Venom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binder (material)
A binder or binding agent is any material or substance that holds or draws other materials together to form a cohesive whole mechanically, chemically, by adhesion or cohesion. More narrowly, binders are liquid or dough-like substances that harden by a chemical or physical process and bind fibres, filler powder and other particles added into it. Examples include glue, adhesive and thickening. Examples of mechanical binders are bond stones in masonry and tie beams in timber framing. Classification Binders are loosely classified as organic ( bitums, animal and plant glues, polymers) and inorganic ( lime, cement, gypsum, liquid glass, etc.). These can be either metallic or ceramic as well as polymeric depending on the nature of the main material. For example, in the compound WC-Co (Tungsten Carbide used in cutting tools) Co constitutes the binding agent for the WC particles. Based on their chemical resistance, binders are classified by the field of use: non-hydrau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kiffa Bead Cylinder
Kiffa () is a large town in the far south region of Mauritania, and the name of an administrative area within the local Assaba Region. Kiffa is located at , some from the coast and at the western end of the Aoukar sand sea of southern Mauritania. Climate Kiffa has a hot desert climate (Köppen climate classification ''BWh''). The climate is Sahelian, with April to June as the hottest months and eighty-five percent of the low annual rainfall occurring from July to September. In the 1990s and early 2000s Kiffa benefited from higher rainfall levels than elsewhere in the western Sahel. While Kiffa benefits from the ongoing "greening of the Sahel" the area's rangeland forage ecosystems remain vulnerable and can be subject to damaging overgrazing. Population, infrastructure and agriculture Kiffa was allowed to grow haphazardly and to sprawl during the later 20th century, and it has continued to do so. Near Kiffa is Kiffa Airport which has a tarmac runway of over 1,600 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
