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Honeycomb Structures
Honeycomb structures are natural or man-made structures that have the geometry of a honeycomb to allow the minimization of the amount of used material to reach minimal weight and minimal material cost. The geometry of honeycomb structures can vary widely but the common feature of all such structures is an array of hollow cells formed between thin vertical walls. The cells are often columnar and hexagonal in shape. A honeycomb shaped structure provides a material with minimal density and relative high out-of-plane compression properties and out-of-plane shear properties. Man-made honeycomb structural materials are commonly made by layering a honeycomb material between two thin layers that provide strength in tension. This forms a plate-like assembly. Honeycomb materials are widely used where flat or slightly curved surfaces are needed and their high specific strength is valuable. They are widely used in the aerospace industry for this reason, and honeycomb materials in alumin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aluminum Honecomb Sheet
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has a great affinity towards oxygen, and forms a protective layer of oxide on the surface when exposed to air. Aluminium visually resembles silver, both in its color and in its great ability to reflect light. It is soft, non-magnetic and ductile. It has one stable isotope, 27Al; this isotope is very common, making aluminium the twelfth most common element in the Universe. The radioactivity of 26Al is used in radiodating. Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al3+ is small and highly charged; as such, it is polarizing, and bonds aluminium forms tend towards covalency. The strong affinity toward ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rock (geology)
In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere. The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy. It may be limited to rocks found on Earth, or it may include planetary geology that studies the rocks of other celestial objects. Rocks are usually grouped into three main groups: igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed when magma cools in the Earth's crust, or lava cools on the ground surface or the seabed. Sedimentary rocks are formed by diagenesis and lithification of sediments, which in turn are formed by the weathering, transport, and deposition of exis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zenodorus (mathematician)
Zenodorus ( el, Ζηνόδωρος; c. 200 – c. 140 BC) was an ancient Greek mathematician. Life and work Little is known about the life of Zenodorus, although he may have befriended Philonides and made two trips to Athens, as described in Philonides' biography. From the style of his writing, it is known that he lived not much later than Archimedes. He is mentioned in Diocles' ''On Burning Mirrors'': And when Zenodorus the astronomer came down to Arcadia and was introduced to us, he asked us how to find a mirror surface such that when it is placed facing the sun the rays reflected from it meet a point and thus cause burning. Zenodorus is known for authoring the treatise ''On isoperimetric figures'', now lost. Many of its propositions are known from Theon of Alexandria's commentary on Ptolemy's ''Syntaxis''. In his ''On isoperimetric figures'', Zenodorus studies the areas and perimeters of different geometric figures. The most important propositions proved by him are that, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euclid
Euclid (; grc-gre, Εὐκλείδης; BC) was an ancient Greek mathematician active as a geometer and logician. Considered the "father of geometry", he is chiefly known for the '' Elements'' treatise, which established the foundations of geometry that largely dominated the field until the early 19th century. His system, now referred to as Euclidean geometry, involved new innovations in combination with a synthesis of theories from earlier Greek mathematicians, including Eudoxus of Cnidus, Hippocrates of Chios, Thales and Theaetetus. With Archimedes and Apollonius of Perga, Euclid is generally considered among the greatest mathematicians of antiquity, and one of the most influential in the history of mathematics. Very little is known of Euclid's life, and most information comes from the philosophers Proclus and Pappus of Alexandria many centuries later. Until the early Renaissance he was often mistaken for the earlier philosopher Euclid of Megara, causing his biogr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marcus Varro
Marcus Terentius Varro (; 116–27 BC) was a Roman polymath and a prolific author. He is regarded as ancient Rome's greatest scholar, and was described by Petrarch as "the third great light of Rome" (after Vergil and Cicero). He is sometimes called Varro Reatinus to distinguish him from his younger contemporary Varro Atacinus. Biography Varro was born in or near Reate (now Rieti) to a family thought to be of equestrian rank, and always remained close to his roots in the area, owning a large farm in the Reatine plain, reported as near Lago di Ripasottile, until his old age. He supported Pompey, reaching the office of praetor, after having been tribune of the people, ''quaestor'' and ''curule aedile''. It is probable that Varro was discontented with the course on which Pompey entered when the First Triumvirate was formed, and he may thus have lost his chance of rising to the consulate. He actually ridiculed the coalition in a work entitled the ''Three-Headed Monster'' ( in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lost Wax Casting
Lost-wax casting (also called "investment casting", "precision casting", or ''cire perdue'' which has been adopted into English from the French, ) is the process by which a duplicate metal sculpture (often silver, gold, brass, or bronze) is cast from an original sculpture. Intricate works can be achieved by this method. The oldest known examples of this technique are approximately 6,500-year-old (4550–4450 BC) and attributed to gold artefacts found at Bulgaria's Varna Necropolis. A copper amulet from Mehrgarh, Indus Valley civilization, in Pakistan, is dated to circa 4,000 BC. Cast copper objects, found in the Nahal Mishmar hoard in southern Israel, which belong to the Chalcolithic period (4500–3500 BC), are estimated, from carbon-14 dating, to date to circa 3500 BC. In Other examples from somewhat later periods are from Mesopotamia in the third millennium BC. Lost-wax casting was widespread in Europe until the 18th century, when a piece-moulding process came to predomi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Daedalus
In Greek mythology, Daedalus (, ; Greek: Δαίδαλος; Latin: ''Daedalus''; Etruscan: ''Taitale'') was a skillful architect and craftsman, seen as a symbol of wisdom, knowledge and power. He is the father of Icarus, the uncle of Perdix, and possibly also the father of Iapyx. Among his most famous creations are the wooden cow for Pasiphaë, the Labyrinth for King Minos of Crete which imprisoned the Minotaur, and wings that he and his son Icarus used to escape Crete. It was during this escape that Icarus did not heed his father's warnings and flew too close to the sun; the wax holding his wings together melted and Icarus fell to his death. Epigraphic evidence The name ''Daidalos'' appears to be attested in Linear B, a writing system used to record Mycenaean Greek. The name appears in the form ''da-da-re-jo-de'', possibly referring to a sanctuary. Family Daedalus's parentage was supplied as a later addition, with various authors attributing different parents to him. His ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Honey Bee
A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosmopolitan distribution of honey bees, introducing multiple subspecies into South America (early 16th century), North America (early 17th century), and Australia (early 19th century). Honey bees are known for their construction of perennial colonial nests from wax, the large size of their colonies, and surplus production and storage of honey, distinguishing their hives as a prized foraging target of many animals, including honey badgers, bears and human hunter-gatherers. Only eight surviving species of honey bee are recognized, with a total of 43 subspecies, though historically 7 to 11 species are recognized. Honey bees represent only a small fraction of the roughly 20,000 known species of bees. The best known honey bee is the western h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanical Load
Mechanical load is the physical stress on a mechanical system or component. Loads can be static or dynamic. Some loads are specified as part of the design criteria of a mechanical system. Depending on the usage, some mechanical loads can be measured by an appropriate test method in a laboratory or in the field. Vehicle It can be the external mechanical resistance against which a machine (such as a motor or engine), acts.American Heritage Dictionary of the English Language. The load can often be expressed as a curve of force versus speed. For instance, a given car traveling on a road of a given slope presents a load which the engine must act against. Because air resistance increases with speed, the motor must put out more torque at a higher speed in order to maintain the speed. By shifting to a higher gear, one may be able to meet the requirement with a higher torque and a lower engine speed, whereas shifting to a lower gear has the opposite effect. Accelerating increases the loa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermoplastics
A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate by intermolecular forces, which weaken rapidly with increased temperature, yielding a viscous liquid. In this state, thermoplastics may be reshaped and are typically used to produce parts by various polymer processing techniques such as injection molding, compression molding, calendering, and extrusion. Thermoplastics differ from thermosetting polymers (or "thermosets"), which form irreversible chemical bonds during the curing process. Thermosets do not melt when heated, but typically decompose and do not reform upon cooling. Above its glass transition temperature and below its melting point, the physical properties of a thermoplastic change drastically without an associated phase change. Some thermoplastics do not fully crystall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paper
Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distributed on the surface, followed by pressing and drying. Although paper was originally made in single sheets by hand, almost all is now made on large machines—some making reels 10 metres wide, running at 2,000 metres per minute and up to 600,000 tonnes a year. It is a versatile material with many uses, including printing, painting, graphics, signage, design, packaging, decorating, writing, and cleaning. It may also be used as filter paper, wallpaper, book endpaper, conservation paper, laminated worktops, toilet tissue, or currency and security paper, or in a number of industrial and construction processes. The papermaking process developed in east Asia, probably China, at least as early as 105 CE, by the Han court eunuch Cai Lun, al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sandwich Core
A sandwich is a food typically consisting of vegetables, sliced cheese or meat, placed on or between slices of bread, or more generally any dish wherein bread serves as a container or wrapper for another food type. The sandwich began as a portable, convenient finger food in the Western world, though over time it has become prevalent worldwide. In the 21st century there has been considerable debate over the precise definition of ''sandwich''; and specifically whether a hot dog or open sandwich can be categorized as such. In the United States, the Department of Agriculture and the Food and Drug Administration are the responsible agencies. The USDA uses the definition, "at least 35% cooked meat and no more than 50% bread" for closed sandwiches, and "at least 50% cooked meat" for open sandwiches. In Britain, the British Sandwich Association defines a sandwich as "any form of bread with a filling, generally assembled cold", a definition which includes wraps and bagels, but exclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
