@a20386
Joined June 2017
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Archimedes pinned down π using straight lines. Polygons inside and outside a circle gave lower and upper bounds on its circumference. Doubling their sides tightened the gap. At 96 sides, he proved 223/71 < π < 22/7.
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周涛 retweeted
Andrei_bt
@AndreiBtvtOct 9
New turret of the T-90M and T-80BVM2 from UKBTM (Unified Turret). The mounting of the Arena-M protective munitions has been changed compared with the 2022 version, see — t.me/btvt2019/1460 The box at the rear of the turret has been reworked: the external ammunition bin has been removed, the equipment module has been changed, and overall the external fittings have been changed significantly. At the same time, the left side of the turret, in terms of counter-munition placement, has remained similar to the old version — with 2 counter-munitions placed behind the turret, where the bin had previously been, while the right side was changed, with 6 counter-munitions placed compactly. And they also hung ERA containers on this mesh to cover the turret–hull junction — a so-so idea. So far, the multiple (threefold) increase in counter-munitions for the Arena-M APS is not apparent.
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There has been much discussion lately about whether & SHOULD the US defend its allies in the WestPac. Some argue that they & the First Island Chain are indefensible. This new Special Report by me and @WilsonCBeaver says otherwise. A thread. heritage.org/defense/report/…
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Wars can represent transitions from one geopolitical era to another, and when they do, they can reshape regional orders even before the fighting ends. Such is the case in the Middle East, which is just three years removed from the Oct. 7 attacks. Though the conflict is ongoing, a post-conflict architecture is already taking shape, one featuring a regional bloc – Turkey, Pakistan and Saudi Arabia – that will have to contend with an Iran mired in massive internal uncertainty. Even so, it will take a long time for Washington to fully remove itself as the region’s primary security guarantor. - Kamran Bokhari geopoliticalfutures.com/the-…
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People often ask about a good book on statistics. Larry Wasserman is in my opinion one of the best (the best?) statistics professors there . Larry is also the academic ambassador of conformal prediction who was the first to introduce conformal prediction to the leading academia in the USA 🇺🇸. His statistic book is available open access for free and there is also companion R code for the book. #statistics #books
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[Utair] Le 02/10/2026, la compagnie UTair a présenté à Tyumen de nouveaux simulateurs de formation pour équipages de conduite pour l'An-74, le simulateur ATR 72-500 complet et les simulateurs Boeing 737-500/800. (c) Utair
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[MS-21] Le MS-21-310, MS.0012, immatriculé 73055. Il est équipé de 2 PD-14. Il a volé afin d'évaluer les effets de l'électricité statique, du système de gestion de vol (FMS) et des systèmes de radionavigation VOR/DME/APK. 4 vols pour une durée totale d'environ 13 heures.
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[MS-21] Le MS-21-310, S/n MS.0013, immatriculé 73057, 2 réacteurs PD-14 a effectué 15 vols d'une durée totale d'environ 48 heures, permettant d'évaluer les systèmes de climatisation et de régulation automatique de la pression, les performances des systèmes de carburant.
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[MS-21] Des essais sur piste ont également été réalisés afin d'évaluer le système de freinage automatique. Plus de détails dans cet article aviation21.ru/ms-21-dajdzhes…

МС-21 – дайджест за сентябрь-2026 » Авиация России

Сентябрь 2026 года стал для программы МС-21 месяцем, когда серийное производство получило конкретные сроки и объёмы. «Аэрофлот» подписал контракт на 90

aviation21.ru
La souris@La_souris_DAOct 6
[MS-21] Le MS-21-310, S/n MS.0013, immatriculé 73057, 2 réacteurs PD-14 a effectué 15 vols d'une durée totale d'environ 48 heures, permettant d'évaluer les systèmes de climatisation et de régulation automatique de la pression, les performances des systèmes de carburant.
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[Spektr-Avia] Un contrat de secours a été signé pour la peinture de 17 avions MS-21 Le second bâtiment pour accueillir les modèles MS-21-300 et MS-21-400 projet arrêté suite aux sanctions. C'était avec des français Seules les fondations ont été faites
La souris@La_souris_DAOct 7
[Spektr-Avia] Le programme actuel de JSC Spektr-Avia pour l’entretien de la flotte du groupe Aeroflot et les travaux individuels dans le cadre du contrat avec l’usine de Yakovlev serait entièrement réalisé jusqu’à fin 2027. 73online.ru/r/gosalternativa…
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[Izd.23680] La construction du navire de recherche et d'expédition, Izd.23680, Ivan Frolov se déroule comme prévu, son lancement étant programmé pour 2027. C'est ce qu'a annoncé le directeur de l'Institut de recherche arctique et antarctique. dp.ru/a/2026/10/06/nauchnoe-…
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In 1772 an eye operation left Leonhard Euler almost completely blind. He could still do the mathematics. He could not read it or write it. So he needed someone. Not a copyist — someone who could follow him. Euler turned to his old friend Daniel Bernoulli in Basel. Bernoulli knew exactly who to send. Nicolas Fuss arrived in St Petersburg in May 1773. He was eighteen. He stayed for the rest of his life. At Euler’s side he helped push more than 250 papers into print. Not transcription — he developed the ideas, built the tables, worked the examples. Then Euler died in 1783, and the assistant became the scientist. Academician that same year. Professor of mathematics. And from 1800 until his own death in 1826, permanent secretary of the Imperial Academy of Sciences. There is a theorem named after him. A sequence of numbers too. And late in life he did one more thing. He took the algebra he had learned at Euler’s elbow and built it into a course for the schools of the Russian Empire. Three volumes. Algebra. Then geometry. Then the application of algebra to geometry — trigonometry, conic sections, and the foundations of the calculus. That trilogy is where Russian school mathematics begins. Kiselev comes after it. The Soviet school comes after Kiselev. Part I — Algebra, 1820. Four divisions, 59 chapters, 570 sections. From what it means for a letter to stand for a quantity, all the way to the irreducible case of the cubic. Two hundred years. No English edition. Not once. Until today. amazon.com/dp/1809100054 youtube.com/watch?v=vlZfHBlP… russianmathbooks.com
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NEW | SPECIAL REPORT: Russian integration of inexpensive, highly maneuverable quasi-cruise missiles marks a concerning shift toward low-cost, cruise-missile-like weapons that can strain Ukraine’s scarce air defense stocks. Russian quasi-cruise missiles pose an emerging threat that requires serious attention because these weapons bridge the gap between inexpensive and slow one-way attack drones and expensive cruise missiles, allowing Russia to impose additional pressure on Ukrainian air defenses at lower cost. Russian developers are actively expanding production, improving speed and maneuverability, and diversifying launch platforms in an effort to increasingly deploy these weapons in 2027 before Ukraine can field countermeasures at scale. Ukraine and its partners therefore face a limited window to expand the production of low-cost interceptors, electronic warfare (EW), and layered air defenses able to handle cruise-missile-like air threats.
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Modular arithmetic wraps numbers around after a fixed modulus. On a 12-hour clock, repeatedly adding five traces 0, 5, 10, 3, 8, 1, and onward. Because gcd(5,12) = 1, the cycle visits every residue before returning to zero. If the step shared a factor with 12, it would visit only part of the clock. Number theory becomes a visible star polygon.
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A tesseract is the four-dimensional version of a cube. The construction follows a pattern. Move a point to trace a line, move the line sideways to form a square, then move the square in a third perpendicular direction to form a cube. One more perpendicular direction produces a tesseract. The nested cubes represent that fourth direction through projection. The inner cube is not actually smaller, just as the far side of a cube can look smaller in a perspective drawing. Connecting their matching corners completes the structure, with 16 vertices, 32 edges, 24 square faces, and 8 cubic cells. A cube’s boundary consists of squares. A tesseract’s boundary consists of cubes. The picture preserves which corners connect, but cannot show all its true lengths and right angles at once.
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Western schools subtraction worksheets look like a mess. In Russian math one just uses a dot enabling 6-7 year olds to do it at ease. russianmathbooks.com/curricu…
Valeriy M., PhD, MBA, CQF
@predict_addictOct 4
Whilst Berkeley students fail at fractions this is in fact what 7 year olds do in countries like Russia and China.
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69 years of Astronautics! 0n 4 October 1957 the R7 (8K71) rocket launched by Tyuratam, placed into orbit the first satellite ever: Sputnik (PS-1). Since the real first satellite was to be the Sputnik 3 (Object D) not ready, PS-1 was a crash program to beat the American Vanguard.
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Each random walk is jagged and unpredictable, yet many independent walkers form a smooth spreading distribution. For unbiased diffusion in one dimension, mean-square displacement grows as ⟨x²⟩ = 2Dt. Typical distance therefore grows like √t, not t. This connection links microscopic randomness to macroscopic diffusion in heat, molecules, populations, prices, and many stochastic systems.
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周涛 retweeted
charly015@charly0153Oct 4
Algo más sobre el sistema S-500 charly015.blogspot.com/2020/… Foto del radar propiedad de vitalyvk.blogspot.com
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A number can be mathematically happy. Take a positive integer, replace it by the sum of the squares of its digits, and repeat. For 28: 28 → 2² + 8² = 68 68 → 6² + 8² = 100 100 → 1 So 28 is a happy number. But unhappy numbers eventually fall into the cycle 4 → 16 → 37 → 58 → 89 → 145 → 42 → 20 → 4.
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