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🔗 Economics 🔗 Statistics 🔗 Business 🔗 Politics

Goodhart's law is an adage named after economist Charles Goodhart, which has been phrased by Marilyn Strathern as "When a measure becomes a target, it ceases to be a good measure." One way in which this can occur is individuals trying to anticipate the effect of a policy and then taking actions that alter its outcome.

Contrafreeloading is an observed behavior in which an organism, when offered a choice between provided food or food that requires effort to obtain, prefers the food that requires effort.

The term was coined in 1963 by animal psychologist Glen Jensen. In his original study, around 200 rats were given a choice between food in a bowl and a food dispenser which required that the rat step on the pedal a set number of times. In this experiment, Jensen found that the rats chose the foot pedal option as a function of the number of foot presses required to receive the food reward. Similar studies by Jensen and other researchers have since replicated his findings with gerbils and other animals including canines, mice, rats, birds, fish, monkeys and chimpanzees. The only animal that did not display similar behavior was the domesticated cat, which preferred to be served.

🔗 Biography 🔗 London 🔗 Biography/science and academia 🔗 Engineering

Thomas Harold Flowers MBE (22 December 1905 - 28 October 1998) was an English engineer with the British General Post Office. During World War II, Flowers designed and built Colossus, the world's first programmable electronic computer, to help decipher encrypted German messages.

🔗 Russia 🔗 Russia/technology and engineering in Russia 🔗 Physics 🔗 Physics/relativity 🔗 Russia/science and education in Russia

Cherenkov radiation (; Russian: Эффект Вавилова — Черенкова, Vavilov-Cherenkov effect) is electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium at a speed greater than the phase velocity (speed of propagation of a wavefront in a medium) of light in that medium. A classic example of Cherenkov radiation is the characteristic blue glow of an underwater nuclear reactor. Its cause is similar to the cause of a sonic boom, the sharp sound heard when faster-than-sound movement occurs. The phenomenon is named after Soviet physicist Pavel Cherenkov.

🔗 Computing 🔗 Computing/Software 🔗 Computing/Computer science 🔗 Cryptography 🔗 Cryptography/Computer science 🔗 Computing/Computer Security

Post-quantum cryptography (sometimes referred to as quantum-proof, quantum-safe or quantum-resistant) refers to cryptographic algorithms (usually public-key algorithms) that are thought to be secure against an attack by a quantum computer. As of 2019, this is not true for the most popular public-key algorithms, which can be efficiently broken by a sufficiently strong quantum computer. The problem with currently popular algorithms is that their security relies on one of three hard mathematical problems: the integer factorization problem, the discrete logarithm problem or the elliptic-curve discrete logarithm problem. All of these problems can be easily solved on a sufficiently powerful quantum computer running Shor's algorithm. Even though current, publicly known, experimental quantum computers lack processing power to break any real cryptographic algorithm, many cryptographers are designing new algorithms to prepare for a time when quantum computing becomes a threat. This work has gained greater attention from academics and industry through the PQCrypto conference series since 2006 and more recently by several workshops on Quantum Safe Cryptography hosted by the European Telecommunications Standards Institute (ETSI) and the Institute for Quantum Computing.

In contrast to the threat quantum computing poses to current public-key algorithms, most current symmetric cryptographic algorithms and hash functions are considered to be relatively secure against attacks by quantum computers. While the quantum Grover's algorithm does speed up attacks against symmetric ciphers, doubling the key size can effectively block these attacks. Thus post-quantum symmetric cryptography does not need to differ significantly from current symmetric cryptography. See section on symmetric-key approach below.

🔗 Computing

Constraint logic programming is a form of constraint programming, in which logic programming is extended to include concepts from constraint satisfaction. A constraint logic program is a logic program that contains constraints in the body of clauses. An example of a clause including a constraint is A(X,Y) :- X+Y>0, B(X), C(Y). In this clause, X+Y>0 is a constraint; A(X,Y), B(X), and C(Y) are literals as in regular logic programming. This clause states one condition under which the statement A(X,Y) holds: X+Y is greater than zero and both B(X) and C(Y) are true.

As in regular logic programming, programs are queried about the provability of a goal, which may contain constraints in addition to literals. A proof for a goal is composed of clauses whose bodies are satisfiable constraints and literals that can in turn be proved using other clauses. Execution is performed by an interpreter, which starts from the goal and recursively scans the clauses trying to prove the goal. Constraints encountered during this scan are placed in a set called constraint store. If this set is found out to be unsatisfiable, the interpreter backtracks, trying to use other clauses for proving the goal. In practice, satisfiability of the constraint store may be checked using an incomplete algorithm, which does not always detect inconsistency.

🔗 Germany

The Nazi book burnings were a campaign conducted by the German Student Union (the "DSt") to ceremonially burn books in Nazi Germany and Austria in the 1930s. The books targeted for burning were those viewed as being subversive or as representing ideologies opposed to Nazism. These included books written by Jewish, pacifist, religious, liberal, anarchist, socialist, communist, and sexologist authors among others. The first books burned were those of Karl Marx and Karl Kautsky.

🔗 Brands 🔗 Toys

Spirograph is a geometric drawing device that produces mathematical roulette curves of the variety technically known as hypotrochoids and epitrochoids. The well known toy version was developed by British engineer Denys Fisher and first sold in 1965.

The name has been a registered trademark of Hasbro Inc. since 1998 following purchase of the company that had acquired the Denys Fisher company. The Spirograph brand was relaunched worldwide in 2013, with its original product configurations, by Kahootz Toys.

🔗 Computing 🔗 Computing/Software

In software development, the yo-yo problem is an anti-pattern that occurs when a programmer has to read and understand a program whose inheritance graph is so long and complicated that the programmer has to keep flipping between many different class definitions in order to follow the control flow of the program. It often happens in object-oriented programming. The term comes from comparing the bouncing attention of the programmer to the up-down movement of a toy yo-yo. Taenzer, Ganti, and Podar described the problem by name, explaining: "Often we get the feeling of riding a yoyo when we try to understand one of these message trees."

Most practices of object-oriented programming recommend keeping the inheritance graph as shallow as possible, in part to avoid this problem. The use of composition instead of inheritance is also strongly preferred, although this still requires that a programmer keep multiple class definitions in mind at once.

More generally, the yo-yo problem can also refer to any situation where a person must keep flipping between different sources of information in order to understand a concept.

Object-oriented design techniques such as documenting layers of the inheritance hierarchy can reduce the effect of this problem, as they collect in one place the information that the programmer is required to understand.

🔗 Psychology 🔗 Sociology

The Ringelmann effect is the tendency for individual members of a group to become increasingly less productive as the size of their group increases. This effect, discovered by French agricultural engineer Maximilien Ringelmann (1861–1931), illustrates the inverse relationship that exists between the size of a group and the magnitude of group members’ individual contribution to the completion of a task. While studying the relationship between process loss (i.e., reductions in performance effectiveness or efficiency) and group productivity, Ringelmann (1913) found that having group members work together on a task (e.g., pulling a rope) actually results in significantly less effort than when individual members are acting alone. Ringelmann discovered that as more and more people are added to a group, the group often becomes increasingly inefficient, ultimately violating the notion that group effort and team participation reliably leads to increased effort on behalf of the members.