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🔗 Technology 🔗 Electronics 🔗 Electrical engineering

A ferrite bead (also known as a ferrite block, ferrite core, ferrite ring, EMI filter, or ferrite choke) is a type of choke that suppresses high-frequency electronic noise in electronic circuits.

Ferrite beads employ high-frequency current dissipation in a ferrite ceramic to build high-frequency noise suppression devices.

🔗 Marine life 🔗 Animals

Deepstaria enigmatica is a very rarely seen giant jellyfish of the family Ulmaridae first described in 1967 by F. S. Russell.

🔗 Computing 🔗 Lists 🔗 Java

This article provides non-exhaustive lists of Java SE Java virtual machines (JVMs). It does not include a large number of Java ME vendors. Note that Java EE runs on the standard Java SE JVM but that some vendors specialize in providing a modified JVM optimized for Java EE applications. A large amount of Java development work takes place on Windows, Solaris, Linux and FreeBSD, primarily with the Oracle JVMs. Note the further complication of different 32-bit/64-bit varieties.

The primary reference Java VM implementation is HotSpot, produced by Oracle Corporation.

🔗 France 🔗 Military history 🔗 Architecture 🔗 Military history/Fortifications 🔗 Military history/French military history 🔗 Archaeology 🔗 Military history/Medieval warfare 🔗 Metalworking 🔗 Military history/European military history 🔗 Woodworking

Guédelon Castle (Château de Guédelon) is a castle currently under construction near Treigny, France. The castle is the focus of an experimental archaeology project aimed at recreating a 13th-century castle and its environment using period technique, dress, and material.

In order to fully investigate the technology required in the past, the project is using only period construction techniques, tools, and costumes. Materials, including wood and stone, are all obtained locally. Jacques Moulin, chief architect for the project, designed the castle according to the architectural model developed during the 12th and 13th centuries by Philip II of France.

Construction started in 1997 under Michel Guyot, owner of Château de Saint-Fargeau, a castle in Saint-Fargeau 13 kilometres away. The site was chosen according to the availability of construction materials: an abandoned stone quarry, in a large forest, with a nearby pond. The site is in a rural woodland area and the nearest town is Saint-Sauveur-en-Puisaye, about 5 kilometres (3.1 mi) to the northeast.

🔗 Classical Greece and Rome 🔗 Board and table games

Ludus latrunculorum, latrunculi, or simply latrones (“the game of brigands”, from latrunculus, diminutive of latro, mercenary or highwayman) was a two-player strategy board game played throughout the Roman Empire. It is said to resemble chess or draughts, but is generally accepted to be a game of military tactics. Because of the scarcity of sources, reconstruction of the game's rules and basic structure is difficult, and therefore there are multiple interpretations of the available evidence.

🔗 Europe 🔗 Musical Instruments 🔗 Percussion

A pyrophone, also known as a "fire/explosion organ" or "fire/explosion calliope" is a musical instrument in which notes are sounded by explosions, or similar forms of rapid combustion, rapid heating, or the like, such as burners in cylindrical glass tubes, creating light and sound. It was invented by physicist and musician Georges Frédéric Eugène Kastner (born 1852 in Strasbourg, France – died 1882 in Bonn, Germany), son of composer Jean-Georges Kastner, around 1870.

🔗 History 🔗 Military history 🔗 Military history/Early Modern warfare 🔗 European history

The "General Crisis" is the term used by some historians to describe the period of widespread conflict and instability that occurred from the early 17th century to the early 18th century in Europe and in more recent historiography in the world at large. The concept is much debated by historians; there is no consensus.

The term was coined by Eric Hobsbawm in his pair of 1954 articles entitled "The Crisis of the Seventeenth Century" published in Past and Present.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Geology 🔗 Explosives

Tired mountain syndrome is a condition in which underground nuclear testing fractures and weakens rock, increasing permeability and the risk of release of radionuclides and radioactive contamination of the environment. Locations said to have undergone the syndrome include the French Polynesian island of Moruroa, Rainier Mesa in the United States, the Dnepr 1 nuclear test site on the Kola Peninsula in Russia, possibly Mount Lazarev in the Novaya Zemlya Test Site in Russia, and Mount Mantap in North Korea.

🔗 Finance & Investment 🔗 COVID-19 🔗 Economics

The 2020 stock market crash is a global stock market crash that began on 20 February, 2020. On 12 February, the Dow Jones Industrial Average, the NASDAQ Composite, and S&P 500 Index all finished at record highs (while the NASDAQ and S&P 500 reached subsequent record highs on 19 February). From 24 to 28 February, stock markets worldwide reported their largest one-week declines since the 2008 financial crisis, thus entering a correction. Global markets into early March became extremely volatile, with large swings occurring in global markets. On 9 March, most global markets reported severe contractions, mainly in response to the 2019–20 coronavirus pandemic and an oil price war between Russia and the OPEC countries led by Saudi Arabia. This became colloquially known as Black Monday I, and at the time was the worst drop since the Great Recession in 2008.

Three days after Black Monday I there was another drop, Black Thursday, where stocks across Europe and North America fell more than 9%. Wall Street experienced its largest single-day percentage drop since Black Monday in 1987, and the FTSE MIB of the Borsa Italiana fell nearly 17%, becoming the worst-hit market during Black Thursday. Despite a temporary rally on 13 March (with markets posting their best day since 2008), all three Wall Street indexes fell more than 12% when markets re-opened on 16 March. At least one benchmark stock market index in all G7 countries and 14 of the G20 countries have been declared to be in bear markets.

As of March 2020, global stocks have seen a downturn of at least 25% during the crash, and 30% in most G20 nations. Goldman Sachs has warned that the US GDP will shrink 29% by the end of the 2nd quarter of 2020, and that unemployment may skyrocket to at least 9%. Australian Prime Minister Scott Morrison has called the looming economic crisis 'akin to the Great Depression'.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Systems 🔗 Systems/Systems engineering

The OODA loop is the cycle observe–orient–decide–act, developed by military strategist and United States Air Force Colonel John Boyd. Boyd applied the concept to the combat operations process, often at the operational level during military campaigns. It is now also often applied to understand commercial operations and learning processes. The approach explains how agility can overcome raw power in dealing with human opponents. It is especially applicable to cyber security and cyberwarfare.

The OODA loop has become an important concept in litigation, business, law enforcement, management education, and military strategy. According to Boyd, decision-making occurs in a recurring cycle of observe–orient–decide–act. An entity (whether an individual or an organization) that can process this cycle quickly, observing and reacting to unfolding events more rapidly than an opponent, can thereby "get inside" the opponent's decision cycle and gain the advantage.