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History of Telecommunication
The history of telecommunication began with the use of smoke signals and drums in Africa, the Americas and parts of Asia. In the 1790s, the first fixed semaphore systems emerged in Europe; however it was not until the 1830s that electrical telecommunication systems started to appear. This article details the history of telecommunication and the individuals who helped make telecommunication systems what they are today. The history of telecommunication is an important part of the larger history of communication.
  • 30.6K
  • 05 Feb 2024
Topic Review
Multi-Anvil Press
The multi-anvil press is a type of device designed to produce extremely high pressures in a relatively small volume. This type of anvil press is used in materials science and geology for the synthesis and study of solid phase materials under extreme pressure, as well as for the industrial production of valuable minerals, especially synthetic diamonds. These instruments allow the simultaneous compression and heating of millimeter size solid phase samples such as rocks, minerals, ceramics, glasses, composite materials, or metal alloys and are capable of reaching pressures above 25 GPa and temperatures exceeding 2500 °C. This allows mineral physicists and petrologists studying the Earth’s interior to experimentally reproduce the conditions found throughout the lithosphere and upper mantle, to a depth of 700 km (citation, figure 1,2). Diamond anvil cells and light-gas guns can access even higher pressures, but the multi-anvil apparatus can accommodate much larger samples, which simplifies sample preparation and improves the precision of measurements and the stability of the experimental parameters (citation needed).
  • 1.3K
  • 17 Nov 2022
Topic Review
Lagrangian Point
In celestial mechanics, the Lagrangian points (/ləˈɡrɑːndʒiən/ also Lagrange points, L-points, or libration points) are the points near two large bodies in orbit where a smaller object will maintain its position relative to the large orbiting bodies. At other locations, a small object would go into its own orbit around one of the large bodies, but at the Lagrangian points the gravitational forces of the two large bodies, the centripetal force of orbital motion, and (for certain points) the Coriolis acceleration all match up in a way that cause the small object to maintain a stable or nearly stable position relative to the large bodies. There are five such points, labeled L1 to L5, all in the orbital plane of the two large bodies, for each given combination of two orbital bodies. For instance, there are five Lagrangian points L1 to L5 for the Sun–Earth system, and in a similar way there are five different Lagrangian points for the Earth–Moon system. L1, L2, and L3 are on the line through the centers of the two large bodies, while L4 and L5 each act as the third vertex of an equilateral triangle formed with the centers of the two large bodies. L4 and L5 are stable, which implies that objects can orbit around them in a rotating coordinate system tied to the two large bodies. Several planets have trojan satellites near their L4 and L5 points with respect to the Sun. Jupiter has more than a million of these trojans. Artificial satellites have been placed at L1 and L2 with respect to the Sun and Earth, and with respect to the Earth and the Moon. The Lagrangian points have been proposed for uses in space exploration.
  • 5.6K
  • 17 Nov 2022
Topic Review
Theodore Roosevelt National Park
Theodore Roosevelt National Park is an American national park comprising three geographically separated areas of badlands in western North Dakota. The park was named for U.S. President Theodore Roosevelt. The park covers 70,446 acres (110.072 sq mi; 28,508 ha; 285.08 km2) of land in three sections: the North Unit, the South Unit, and the Elkhorn Ranch Unit. The park's larger South Unit lies alongside Interstate 94 near Medora, North Dakota. The smaller North Unit is situated about 80 mi (130 km) north of the South Unit, on U.S. Highway 85, just south of Watford City, North Dakota. Roosevelt's Elkhorn Ranch is located between the North and South units, approximately 20 mi (32 km) west of US 85 and Fairfield, North Dakota. The Little Missouri River flows through all three units of the park. The Maah Daah Hey Trail connects all three units. The park received 708,003 recreational visitors in 2017. It is the only American national park named directly after a single person.
  • 1.3K
  • 22 Nov 2022
Topic Review
Suetonius on Christians
The Roman historian Suetonius (c. AD 69 – c. AD 122) mentions early Christians and may refer to Jesus Christ in his work Lives of the Twelve Caesars. One passage in the biography of the Emperor Claudius Divus Claudius 25, refers to agitations in the Roman Jewish community and the expulsion of Jews from Rome by Claudius during his reign (AD 41 to AD 54), which may be the expulsion mentioned in the Acts of the Apostles (18:2). In this context "Chresto" is mentioned. Some scholars see this as a likely reference to Jesus, while others see it as referring to an otherwise unknown person living in Rome. Christians are explicitly mentioned in Suetonius' biography of the Emperor Nero (Nero 16) as among those punished during Nero's reign. These punishments are generally dated to around AD 64, the year of the Great Fire of Rome. In this passage Suetonius describes Christianity as excessive religiosity (superstitio) as do his contemporaries, Tacitus and Pliny. Historians debate whether or not the Roman government distinguished between Christians and Jews prior to Nerva's modification of the Fiscus Judaicus in AD 96. From then on, practising Jews paid the tax, Christians did not.
  • 17.7K
  • 17 Nov 2022
Topic Review
Caisson (Engineering)
In geotechnical engineering, a caisson (/ˈkeɪsən/ or /ˈkeɪsɒn/) is a watertight retaining structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam, or for the repair of ships. These are constructed such that the water can be pumped out, keeping the working environment dry. When piers are being built using an open caisson, and it is not practical to reach suitable soil, friction pilings may be driven to form a suitable sub-foundation. These piles are connected by a foundation pad upon which the column pier is erected.
  • 1.7K
  • 22 Nov 2022
Topic Review
Bodhi
The English term enlightenment is the western translation of the abstract noun bodhi, (/ˈboʊdi/; Sanskrit: बोधि; Pali: bodhi), the knowledge or wisdom, or awakened intellect, of a Buddha. The verbal root budh- means "to awaken," and its literal meaning is closer to "awakening." Although the term buddhi is also used in other Indian philosophies and traditions, its most common usage is in the context of Buddhism. The term "enlightenment" was popularised in the Western world through the 19th century translations of Max Müller. It has the western connotation of general insight into transcendental truth or reality. The term is also being used to translate several other Buddhist terms and concepts, which are used to denote (initial) insight (prajna (Sanskrit), wu (Chinese), kensho and satori(Japanese)); knowledge (vidhya); the "blowing out" (Nirvana) of disturbing emotions and desires and the subsequent freedom or release (vimukti); and the attainment of supreme Buddhahood (samyak sam bodhi), as exemplified by Gautama Buddha. What exactly constituted the Buddha's awakening is unknown. It may probably have involved the knowledge that liberation was attained by the combination of mindfulness and dhyāna, applied to the understanding of the arising and ceasing of craving. The relation between dhyana and insight is a core problem in the study of Buddhism, and is one of the fundamentals of Buddhist practice. In the western world the concept of (spiritual) enlightenment has taken on a romantic meaning. It has become synonymous with self-realization and the true self and false self, being regarded as a substantial essence being covered over by social conditioning.
  • 6.4K
  • 22 Nov 2022
Topic Review
Crown Rabbi (Russia)
Crown rabbi (Russian: казённый раввин) was a position in the Russian Empire given to a member of a Jewish community appointed to act as an intermediary between his community and the Imperial government, to perform certain civil duties such as registering births, marriages, and divorces. Because their main job qualification was fluency in Russian, crown rabbis were typically considered agents of the state by members of their own communities, not true rabbis, and they often had no education in or knowledge of Jewish law.
  • 706
  • 17 Nov 2022
Topic Review
Non-Standard Analysis
The history of calculus is fraught with philosophical debates about the meaning and logical validity of fluxions or infinitesimal numbers. The standard way to resolve these debates is to define the operations of calculus using epsilon–delta procedures rather than infinitesimals. Non-standard analysis instead reformulates the calculus using a logically rigorous notion of infinitesimal numbers. Non-standard analysis was originated in the early 1960s by the mathematician Abraham Robinson. He wrote: "... the idea of infinitely small or infinitesimal quantities seems to appeal naturally to our intuition. At any rate, the use of infinitesimals was widespread during the formative stages of the Differential and Integral Calculus. As for the objection ... that the distance between two distinct real numbers cannot be infinitely small, Gottfried Wilhelm Leibniz argued that the theory of infinitesimals implies the introduction of ideal numbers which might be infinitely small or infinitely large compared with the real numbers but which were to possess the same properties as the latter". Robinson argued that this law of continuity of Leibniz's is a precursor of the transfer principle. Robinson continued: "However, neither he nor his disciples and successors were able to give a rational development leading up to a system of this sort. As a result, the theory of infinitesimals gradually fell into disrepute and was replaced eventually by the classical theory of limits." "It is shown in this book that Leibniz's ideas can be fully vindicated and that they lead to a novel and fruitful approach to classical Analysis and to many other branches of mathematics. The key to our method is provided by the detailed analysis of the relation between mathematical languages and mathematical structures which lies at the bottom of contemporary model theory." In 1973, intuitionist Arend Heyting praised non-standard analysis as "a standard model of important mathematical research".
  • 1.6K
  • 17 Nov 2022
Topic Review
Autism and Working Memory
Autism is a variation of neural development diagnosed as impaired social interaction and communication, and by restricted and repetitive behavior. In this article, the word autism is used for referring to the whole range of variations on the autism spectrum, which is not uncommon. Working memory is the system that actively holds multiple pieces of transitory information in the mind, where they can be manipulated. This system has a limited capacity. Working memory is a part of the executive functions (EF), an umbrella term for cognitive processes that regulate, control, and manage other cognitive processes, for instance planning and attention.
  • 1.5K
  • 17 Nov 2022
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