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🔗 Computing 🔗 Systems 🔗 Business 🔗 Computing/Software 🔗 Computing/Computer science 🔗 Engineering 🔗 Systems/Systems engineering

Hofstadter's law is a self-referential adage, coined by Douglas Hofstadter in his book Gödel, Escher, Bach: An Eternal Golden Braid (1979) to describe the widely experienced difficulty of accurately estimating the time it will take to complete tasks of substantial complexity:

Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law.

The law is often cited by programmers in discussions of techniques to improve productivity, such as The Mythical Man-Month or extreme programming.

🔗 Mathematics

Sexy primes are prime numbers that differ from each other by 6. For example, the numbers 5 and 11 are both sexy primes, because 11 - 5 = 6.

The term "sexy prime" is a pun stemming from the Latin word for six: sex.

If p + 2 or p + 4 (where p is the lower prime) is also prime, then the sexy prime is part of a prime triplet.

🔗 Mathematics

Fractional calculus is a branch of mathematical analysis that studies the several different possibilities of defining real number powers or complex number powers of the differentiation operator D

${\displaystyle Df(x)={\frac {d}{dx}}f(x)\,,}$

and of the integration operator J

${\displaystyle Jf(x)=\int _{0}^{x}f(s)\,ds\,,}$

and developing a calculus for such operators generalizing the classical one.

In this context, the term powers refers to iterative application of a linear operator D to a function f, that is, repeatedly composing D with itself, as in ${\displaystyle D^{2}(f)=(D\circ D)(f)=D(D(f))}$.

For example, one may ask for a meaningful interpretation of:

${\displaystyle {\sqrt {D}}=D^{\frac {1}{2}}}$

as an analogue of the functional square root for the differentiation operator, that is, an expression for some linear operator that when applied twice to any function will have the same effect as differentiation. More generally, one can look at the question of defining a linear functional

${\displaystyle D^{a}}$

for every real-number a in such a way that, when a takes an integer value n ∈ ℤ, it coincides with the usual n-fold differentiation D if n > 0, and with the −nth power of J when n < 0.

One of the motivations behind the introduction and study of these sorts of extensions of the differentiation operator D is that the sets of operator powers { D^a |a ∈ ℝ } defined in this way are continuous semigroups with parameter a, of which the original discrete semigroup of { Dⁿ | n ∈ ℤ } for integer n is a denumerable subgroup: since continuous semigroups have a well developed mathematical theory, they can be applied to other branches of mathematics.

Fractional differential equations, also known as extraordinary differential equations, are a generalization of differential equations through the application of fractional calculus.

🔗 Mass surveillance 🔗 Sociology

The small-world experiment comprised several experiments conducted by Stanley Milgram and other researchers examining the average path length for social networks of people in the United States. The research was groundbreaking in that it suggested that human society is a small-world-type network characterized by short path-lengths. The experiments are often associated with the phrase "six degrees of separation", although Milgram did not use this term himself.

The Squarial (a portmanteau of the words square and aerial) was a satellite antenna used for reception of the now defunct British Satellite Broadcasting television service (BSB). The Squarial was a flat plate satellite antenna, built to be unobtrusive and unique. BSB were counting on the form factor of the antenna to clearly differentiate themselves from their competitors at the time. At the time of development, satellite installations usually required a 90 cm dish in order to receive a clear signal from the transmitting satellite. The smaller antenna was BSB's unique selling point and was heavily advertised in order to attract customers to their service.

🔗 History of Science 🔗 Robotics

Leachim was an early example of Diphone synthetic speech and demonstrated how voice branching could be done quickly via computer discs to create understandable speech (i.e. verbal output). This method combined phonemes, words, and sentences to form verbal responsive messages when prompted by the computer. The device received attention on a world-wide basis because hundreds of articles were written about it.

🔗 California 🔗 California/San Francisco Bay Area 🔗 Engineering

The San Jose electric light tower, also known as Owen's Electric Tower after its creator and chief booster, was constructed in 1881 at an intersection in downtown San Jose, California, as a "high light" or moonlight tower to light the city using arc lights. A pioneer use of electricity for municipal lighting, it was later strung with incandescent bulbs and was destroyed in a storm in December 1915. A half-size replica stands at History Park at Kelley Park.

🔗 Medicine 🔗 Psychology

Capgras delusion is a psychiatric disorder in which a person holds a delusion that a friend, spouse, parent, or other close family member (or pet) has been replaced by an identical impostor. It is named after Joseph Capgras (1873–1950), a French psychiatrist.

The Capgras delusion is classified as a delusional misidentification syndrome, a class of delusional beliefs that involves the misidentification of people, places, or objects. It can occur in acute, transient, or chronic forms. Cases in which patients hold the belief that time has been "warped" or "substituted" have also been reported.

The delusion most commonly occurs in individuals diagnosed with paranoid schizophrenia but has also been seen in brain injury, dementia with Lewy bodies, and other dementia. It presents often in individuals with a neurodegenerative disease, particularly at an older age. It has also been reported as occurring in association with diabetes, hypothyroidism, and migraine attacks. In one isolated case, the Capgras delusion was temporarily induced in a healthy subject by the drug ketamine. It occurs more frequently in females, with a female to male ratio of approximately 3 to 2.

🔗 Computing 🔗 Computing/Computer science

In computer programming, a rope, or cord, is a data structure composed of smaller strings that is used to efficiently store and manipulate a very long string. For example, a text editing program may use a rope to represent the text being edited, so that operations such as insertion, deletion, and random access can be done efficiently.

🔗 Video games

Bob's Game (stylized as "bob's game") was a role-playing video game being developed by independent video game developer Robert Pelloni since 2003/2004. The project is most notable for Pelloni developing the game using open source software development tools and Nintendo's refusal to license him the official SDK as well as Bob's response to that decision.