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🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/Asian military history 🔗 Military history/Southeast Asian military history 🔗 Vietnam

Operation Popeye (Project Controlled Weather Popeye / Motorpool / Intermediary-Compatriot) was a highly classified weather modification program in Southeast Asia during 1967–1972. The cloud seeding operation during the Vietnam War ran from March 20, 1967 until July 5, 1972 in an attempt to extend the monsoon season, specifically over areas of the Ho Chi Minh Trail. The operation was used to induce rain and extend the East Asian Monsoon season in support of U.S. government efforts related to the War in Southeast Asia.

The former U.S. Secretary of Defense, Robert S. McNamara, was aware that there might be objections raised by the international scientific community but said in a memo to the president that such objections had not in the past been a basis for prevention of military activities considered to be in the interests of U.S. national security.

The chemical weather modification program was conducted from Thailand over Cambodia, Laos, and Vietnam and allegedly sponsored by Secretary of State Henry Kissinger and CIA without the authorization of then Secretary of Defense Melvin Laird who had categorically denied to Congress that a program for modification of the weather for use as a tactical weapon even existed.

🔗 Television

TV detector vans are vans, which, according to the BBC, contain equipment that can detect the presence of television sets in use. The vans are operated by contractors working for the BBC, to enforce the television licensing system in the UK, the Channel Islands and on the Isle of Man. The veracity of their operation has been called into question in the media.

🔗 History 🔗 Germany 🔗 Politics 🔗 Austria 🔗 European history 🔗 Animal rights 🔗 Former countries

There was widespread support for animal welfare in Nazi Germany (German: Tierschutz im nationalsozialistischen Deutschland) among the country's leadership. Adolf Hitler and his top officials took a variety of measures to ensure animals were protected.

Several Nazis were environmentalists, and species protection and animal welfare were significant issues in the Nazi regime. Heinrich Himmler made an effort to ban the hunting of animals. Hermann Göring was a professed animal lover and conservationist, who, on instructions from Hitler, committed Germans who violated Nazi animal welfare laws to concentration camps. In his private diaries, Nazi Propaganda Minister Joseph Goebbels described Hitler as a vegetarian whose hatred of the Jewish religion in large part stemmed from the ethical distinction this faith drew between the value of humans and the value of other animals; Goebbels also mentions that Hitler planned to ban slaughterhouses in the German Reich following the conclusion of World War II. Nevertheless, animal testing was common in Nazi Germany.

The current animal welfare laws in Germany were initially introduced by the Nazis.

🔗 Cats 🔗 Malaysia

Operation Cat Drop is the name given to the delivery of some 14,000 cats by the United Kingdom's Royal Air Force to remote regions of the then-British colony of Sarawak (today part of Malaysia), on the island of Borneo in 1960. The cats were flown out of Singapore and delivered in crates dropped by parachutes as part of a broader program of supplying cats to combat a plague of rats. The operation was reported as a "success" at the time. Some newspaper reports published soon after the Operation reference only 23 cats being used. However, later reports state as many as 14,000 cats were used. An additional source references a "recruitment" drive for 30 cats a few days prior to Operation Cat Drop.

🔗 Cryptography 🔗 Cryptography/Computer science 🔗 Numismatics 🔗 Numismatics/Cryptocurrency

Hashcash is a proof-of-work system used to limit email spam and denial-of-service attacks, and more recently has become known for its use in bitcoin (and other cryptocurrencies) as part of the mining algorithm. Hashcash was proposed in 1997 by Adam Back and described more formally in Back's 2002 paper "Hashcash - A Denial of Service Counter-Measure".

🔗 Computer science 🔗 Economics 🔗 Engineering 🔗 Gender Studies

Pareto efficiency or Pareto optimality is a situation where no action or allocation is available that makes one individual better off without making another worse off. The concept is named after Vilfredo Pareto (1848–1923), Italian civil engineer and economist, who used the concept in his studies of economic efficiency and income distribution. The following three concepts are closely related:

• Given an initial situation, a Pareto improvement is a new situation where some agents will gain, and no agents will lose.
• A situation is called Pareto-dominated or Pareto-inefficient if there is some possible Pareto improvement that has not been made.
• A situation is called Pareto-optimal or Pareto-efficient if no change could lead to improved satisfaction for some agent without some other agent losing or, equivalently, if there is no scope for further Pareto improvement (in other words, the situation is not Pareto-dominated).

The Pareto front (also called Pareto frontier or Pareto set) is the set of all Pareto-efficient situations.

Pareto originally used the word "optimal" for the concept, but as it describes a situation where a limited number of people will be made better off under finite resources, and it does not take equality or social well-being into account, it is in effect a definition of and better captured by "efficiency".

In addition to the context of efficiency in allocation, the concept of Pareto efficiency also arises in the context of efficiency in production vs. x-inefficiency: a set of outputs of goods is Pareto-efficient if there is no feasible re-allocation of productive inputs such that output of one product increases while the outputs of all other goods either increase or remain the same.

Pareto efficiency is measured along the production possibility frontier (PPF), which is a graphical representation of all the possible options of output for two products that can be produced using all factors of production.

Besides economics, the notion of Pareto efficiency has been applied to the selection of alternatives in engineering and biology. Each option is first assessed, under multiple criteria, and then a subset of options is ostensibly identified with the property that no other option can categorically outperform the specified option. It is a statement of impossibility of improving one variable without harming other variables in the subject of multi-objective optimization (also termed Pareto optimization).

🔗 Computing 🔗 Telecommunications

Gemini space denotes the whole of the public information that is published on the Internet by the Gemini community via the Gemini protocol. Thus, Gemini spans an alternative communication web, with hypertext documents that include hyperlinks to other resources that the user can easily access, similar to the secure version of the Hypertext Transfer Protocol (HTTPS), but with a focus on simplified information sharing, both in respect to creation and reading of Gemini content.

🔗 Physics 🔗 Geology 🔗 Physics/Acoustics

Singing sand, also called whistling sand, barking sand or singing dune, is sand that produces sound. The sound emission may be caused by wind passing over dunes or by walking on the sand.

Certain conditions have to come together to create singing sand:

1. The sand grains have to be round and between 0.1 and 0.5 mm in diameter.
2. The sand has to contain silica.
3. The sand needs to be at a certain humidity.

The most common frequency emitted seems to be close to 450 Hz.

There are various theories about the singing sand mechanism. It has been proposed that the sound frequency is controlled by the shear rate. Others have suggested that the frequency of vibration is related to the thickness of the dry surface layer of sand. The sound waves bounce back and forth between the surface of the dune and the surface of the moist layer, creating a resonance that increases the sound's volume. The noise may be generated by friction between the grains or by the compression of air between them.

Other sounds that can be emitted by sand have been described as "roaring" or "booming".

🔗 Star Trek

The Kobayashi Maru is a training exercise in the fictional Star Trek universe designed to test the character of Starfleet Academy cadets in a no-win scenario. The Kobayashi Maru test was first depicted in the opening scene of the film Star Trek II: The Wrath of Khan and also appears in the 2009 film Star Trek. Screenwriter Jack B. Sowards is credited with inventing the test. The test's name is occasionally used among Star Trek fans or those familiar with the series to describe a no-win scenario, a test of one's character or a solution that involves redefining the problem and managing an insurmountable scenario gracefully.

The notional primary goal of the exercise is to rescue the civilian vessel Kobayashi Maru in a simulated battle with the Klingons. The disabled ship is located in the Klingon Neutral Zone, and any Starfleet ship entering the zone would cause an interstellar border incident. The approaching cadet crew must decide whether to attempt rescue of the Kobayashi Maru crew—endangering their own ship and lives—or leave the Kobayashi Maru to certain destruction. If the cadet chooses to attempt rescue, the simulation is designed to guarantee that the cadet's ship enters a situation that he or she will have absolutely no chance of winning, escaping, negotiating or even surviving.

🔗 Mathematics

The hairy ball theorem of algebraic topology (sometimes called the hedgehog theorem in Europe) states that there is no nonvanishing continuous tangent vector field on even-dimensional n-spheres. For the ordinary sphere, or 2‑sphere, if f is a continuous function that assigns a vector in R³ to every point p on a sphere such that f(p) is always tangent to the sphere at p, then there is at least one p such that f(p) = 0. The theorem was first stated by Henri Poincaré in the late 19th century, and first proven in 1912 by Luitzen Egbertus Jan Brouwer.

The theorem has been expressed colloquially as "you can't comb a hairy ball flat without creating a cowlick" or "you can't comb the hair on a coconut".