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Cracovian Product
In astronomical and geodetic calculations, Cracovians are a clerical convenience introduced in 1925 by Tadeusz Banachiewicz for solving systems of linear equations by hand. Such systems can be written as in matrix notation where x and b are column vectors and the evaluation of b requires the multiplication of the rows of ''A'' by the vector x. Cracovians introduced the idea of using the transpose of ''A'', ''A''T, and multiplying the columns of ''A''T by the column x. This amounts to the definition of a new type of matrix multiplication denoted here by '∧'. Thus . The Cracovian product of two matrices, say ''A'' and ''B'', is defined by , where ''B''T and ''A'' are assumed compatible for the common ( Cayley) type of matrix multiplication. Since , the products and {{nowrap, 1=''A'' ∧ (''B'' ∧ ''C'') will generally be different; thus, Cracovian multiplication is non-associative. Cracovians are an example of a quasigroup. Cracovians adopted a column-row convention for d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomy
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include planets, natural satellite, moons, stars, nebulae, galaxy, galaxies, meteoroids, asteroids, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond atmosphere of Earth, Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Egyptian astronomy, Egyptians, Babylonian astronomy, Babylonians, Greek astronomy, Greeks, Indian astronomy, Indians, Chinese astronomy, Chinese, Maya civilization, M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Tape Data Storage
Magnetic-tape data storage is a system for storing digital information on magnetic tape using digital recording. Tape was an important medium for primary data storage in early computers, typically using large open reels of 7-track, later 9-track tape. Modern magnetic tape is most commonly packaged in cartridges and cassettes, such as the widely supported Linear Tape-Open (LTO) and IBM 3592 series. The device that performs the writing or reading of data is called a tape drive. Autoloaders and tape libraries are often used to automate cartridge handling and exchange. Compatibility was important to enable transferring data. Tape data storage is now used more for system backup, data archive and data exchange. The low cost of tape has kept it viable for long-term storage and archive. Open reels Initially, magnetic tape for data storage was wound on reels. This standard for large computer systems persisted through the late 1980s, with steadily increasing capacity d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrometry
Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other Astronomical object, celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, the Milky Way. History The history of astrometry is linked to the history of star catalogues, which gave astronomers reference points for objects in the sky so they could track their movements. This can be dated back to the ancient Greek astronomer Hipparchus, who around 190 BC used the catalogue of his predecessors Timocharis and Aristillus to discover Earth's precession. In doing so, he also developed the brightness scale still in use today. Hipparchus compiled a catalogue with at least 850 stars and their positions. Hipparchus's successor, Ptolemy, included a catalogue of 1,022 stars in his work the ''Almagest'', giving their location, coordinates, and brightness. In the 10th century, the Iranian astronomer Abd al-Rahman al-Sufi carried ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1751 Herget
1751 Herget, provisional designation , is a stony Gefionian asteroid from the central region of the asteroid belt, approximately 11 kilometers in diameter. It was discovered on 27 July 1955, by IUs Indiana Asteroid Program at Goethe Link Observatory near Brooklyn, Indiana, United States. The asteroid was named after American astronomer Paul Herget. Classification and orbit ''Herget'' is a member of the large Gefion family of asteroids (). It orbits the Sun in the central main-belt at a distance of 2.3–3.3 AU once every 4 years and 8 months (1,701 days; semi-major axis of 2.79 AU). Its orbit has an eccentricity of 0.18 and an inclination of 8 ° with respect to the ecliptic. As no precoveries were taken, and no prior identifications were made, the body's observation arc begins with its official discovery observation at Goethe Link in 1955. Physical characteristics In the SMASS classification, ''Herget'' has been characterized as a common S-type asteroid, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroid
An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). Asteroids are rocky, metallic, or icy bodies with no atmosphere, and are broadly classified into C-type asteroid, C-type (carbonaceous), M-type asteroid, M-type (metallic), or S-type asteroid, S-type (silicaceous). The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across to Ceres (dwarf planet), Ceres, a dwarf planet almost 1000 km in diameter. A body is classified as a comet, not an asteroid, if it shows a coma (tail) when warmed by solar radiation, although recent observations suggest a continuum between these types of bodies. Of the roughly one million known asteroids, the greatest number are located between the orbits of Mars and Jupiter, approximately 2 to 4 astronomical unit, AU ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
R Programming Language
R is a programming language for statistical computing and data visualization. It has been widely adopted in the fields of data mining, bioinformatics, data analysis, and data science. The core R language is extended by a large number of software packages, which contain reusable code, documentation, and sample data. Some of the most popular R packages are in the tidyverse collection, which enhances functionality for visualizing, transforming, and modelling data, as well as improves the ease of programming (according to the authors and users). R is free and open-source software distributed under the GNU General Public License. The language is implemented primarily in C, Fortran, and R itself. Precompiled executables are available for the major operating systems (including Linux, MacOS, and Microsoft Windows). Its core is an interpreted language with a native command line interface. In addition, multiple third-party applications are available as graphical user interf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kraków
, officially the Royal Capital City of Kraków, is the List of cities and towns in Poland, second-largest and one of the oldest cities in Poland. Situated on the Vistula River in Lesser Poland Voivodeship, the city has a population of 804,237 (2023), with approximately 8 million additional people living within a radius. Kraków was the official capital of Poland until 1596, and has traditionally been one of the leading centres of Polish academic, cultural, and artistic life. Cited as one of Europe's most beautiful cities, its Kraków Old Town, Old Town was declared a UNESCO World Heritage Site in 1978, one of the world's first sites granted the status. The city began as a Hamlet (place), hamlet on Wawel Hill and was a busy trading centre of Central Europe in 985. In 1038, it became the seat of King of Poland, Polish monarchs from the Piast dynasty, and subsequently served as the centre of administration under Jagiellonian dynasty, Jagiellonian kings and of the Polish–Lithuan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random Access Memory
Random-access memory (RAM; ) is a form of electronic computer memory that can be read and changed in any order, typically used to store working data and machine code. A random-access memory device allows data items to be read or written in almost the same amount of time irrespective of the physical location of data inside the memory, in contrast with other direct-access data storage media (such as hard disks and magnetic tape), where the time required to read and write data items varies significantly depending on their physical locations on the recording medium, due to mechanical limitations such as media rotation speeds and arm movement. In today's technology, random-access memory takes the form of integrated circuit (IC) chips with MOS (metal–oxide–semiconductor) memory cells. RAM is normally associated with volatile types of memory where stored information is lost if power is removed. The two main types of volatile random-access semiconductor memory are static ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drum Memory
Drum memory was a magnetic data storage device invented by Gustav Tauschek in 1932 in Austria. Drums were widely used in the 1950s and into the 1960s as computer memory. Many early computers, called drum computers or drum machines, used drum memory as the main working memory of the computer. Some drums were also used as Auxiliary memory, secondary storage as for example various IBM_drum_storage, IBM drum storage drives and the UNIVAC FASTRAND series of drums. Drums were displaced as primary computer memory by magnetic core memory, which offered a better balance of size, speed, cost, reliability and potential for further improvements. Drums were then replaced by hard disk drives for secondary storage, which were both less expensive and offered denser storage. The manufacturing of drums ceased in the 1970s. Technical design A drum memory or drum storage unit contained a large metal cylinder, coated on the outside surface with a ferromagnetic recording material. It could be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sequential Access Memory
In computing, sequential access memory (SAM) is a class of data storage devices that read stored data in a sequence. This is in contrast to random access memory (RAM) where data can be accessed in any order. Sequential access devices are usually a form of magnetic storage or optical storage. While sequential access memory is read in sequence, arbitrary locations can still be accessed by "seeking" to the requested location. This operation, however, is often relatively inefficient (see seek time, rotational latency). Magnetic sequential access memory is typically used for secondary storage in general-purpose computers due to their higher density at lower cost compared to RAM, as well as resistance to wear and non-volatility. Magnetic tape is a type of sequential access memory still in use; historically, drum memory has also been used. See also * Sequential access * Basic sequential access method (BSAM) * Queued sequential access method (QSAM) * Secondary storage ** Hard disk ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geodesy
Geodesy or geodetics is the science of measuring and representing the Figure of the Earth, geometry, Gravity of Earth, gravity, and Earth's rotation, spatial orientation of the Earth in Relative change, temporally varying Three-dimensional space, 3D. It is called planetary geodesy when studying other astronomical body, astronomical bodies, such as planets or Natural satellite, circumplanetary systems. Geodynamics, Geodynamical phenomena, including crust (geology), crustal motion, tides, and polar motion, can be studied by designing global and national Geodetic control network, control networks, applying space geodesy and terrestrial geodetic techniques, and relying on Geodetic datum, datums and coordinate systems. Geodetic job titles include geodesist and geodetic surveyor. History Geodesy began in pre-scientific Classical antiquity, antiquity, so the very word geodesy comes from the Ancient Greek word or ''geodaisia'' (literally, "division of Earth"). Early ideas about t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quasigroup
In mathematics, especially in abstract algebra, a quasigroup is an algebraic structure that resembles a group in the sense that " division" is always possible. Quasigroups differ from groups mainly in that the associative and identity element properties are optional. In fact, a nonempty associative quasigroup is a group. A quasigroup that has an identity element is called a loop. Definitions There are at least two structurally equivalent formal definitions of quasigroup: * One defines a quasigroup as a set with one binary operation. * The other, from universal algebra, defines a quasigroup as having three primitive operations. The homomorphic image of a quasigroup that is defined with a single binary operation, however, need not be a quasigroup, in contrast to a quasigroup as having three primitive operations. We begin with the first definition. Algebra A quasigroup is a non-empty set with a binary operation (that is, a magma, indicating that a quasigroup has to sat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
