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π Type A and Type B personality theory
Type A and Type B personality hypothesis describes two contrasting personality types. In this hypothesis, personalities that are more competitive, highly organized, ambitious, impatient, highly aware of time management and/or aggressive are labeled Type A, while more relaxed, less 'neurotic', 'frantic', 'explainable', personalities are labeled Type B.
The two cardiologists who developed this theory came to believe that Type A personalities had a greater chance of developing coronary heart disease. Following the results of further studies and considerable controversy about the role of the tobacco industry funding of early research in this area, some reject, either partially or completely, the link between Type A personality and coronary disease. Nevertheless, this research had a significant effect on the development of the health psychology field, in which psychologists look at how an individual's mental state affects physical health.
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- "Type A and Type B personality theory" | 2014-03-22 | 26 Upvotes 3 Comments
π Vega program
The Vega program (Cyrillic: ΠΠ΅ΠΠ°) was a series of Venus missions that also took advantage of the appearance of comet 1P/Halley in 1986. Vega 1 and Vega 2 were uncrewed spacecraft launched in a cooperative effort among the Soviet Union (who also provided the spacecraft and launch vehicle) and Austria, Bulgaria, France, Hungary, the German Democratic Republic, Poland, Czechoslovakia, and the Federal Republic of Germany in December 1984. They had a two-part mission to investigate Venus and also flyby Halley's Comet.
The flyby of Halley's Comet had been a late mission change in the Venera program following on from the cancellation of the American Halley mission in 1981. A later Venera mission was canceled and the Venus part of the Vega 1 mission was reduced. Because of this, the craft was designated VeGa, a contraction of Venera and Gallei (ΠΠ΅Π½Π΅ΡΠ° and ΠΠ°Π»Π»Π΅Ρ respectively, the Russian words for "Venus" and "Halley"). The spacecraft design was based on the previous Venera 9 and Venera 10 missions.
The two spacecraft were launched on 15 and 21 December 1984, respectively. With their redesignated dual missions, the Vega probes became part of the Halley Armada, a group of space probes that studied Halley's Comet during its 1985/1986 perihelion.
Discussed on
- "Vega program" | 2016-09-12 | 54 Upvotes 4 Comments
π St. Cuthbert's Beads
St. Cuthbert's beads (or Cuddy's beads) are fossilised portions of the "stems" of crinoids from the Carboniferous period. Crinoids are a kind of marine echinoderm which are still extant, and which are sometimes known as "sea lilies". These bead-like fossils are washed out onto the beach and in medieval Northumberland were strung together as necklaces or rosaries, and became associated with St Cuthbert.
In other parts of England, circular crinoid columnals were known as "fairy money." Pentagonal crinoid columnals were known as "star stones", and moulds of the stems left impressions which were known as screwstones. In Germany, the columnals were known as Bonifatius pfennige (St Boniface's pennies) and in America they are known as Indian beads.
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- "St. Cuthbert's Beads" | 2022-08-31 | 36 Upvotes 11 Comments
π Beatrice the Sixteenth
Beatrice the Sixteenth: Being the Personal Narrative of Mary Hatherley, M.B., Explorer and Geographer is a 1909 feminist utopian novel by the English transgender lawyer and writer Irene Clyde, about a time traveller who discovers a lost world, which is an egalitarian postgender society.
Discussed on
- "Beatrice the Sixteenth" | 2020-09-22 | 55 Upvotes 36 Comments
π Vacuum airship
A vacuum airship, also known as a vacuum balloon, is a hypothetical airship that is evacuated rather than filled with a lighter-than-air gas such as hydrogen or helium. First proposed by Italian Jesuit priest Francesco Lana de Terzi in 1670, the vacuum balloon would be the ultimate expression of lifting power per volume displaced.
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- "Vacuum Airship" | 2023-07-20 | 101 Upvotes 73 Comments
- "Vacuum airship" | 2014-08-12 | 56 Upvotes 59 Comments
π Wikipedia: Cost of Electricity by Source
Different methods of electricity generation can incur significantly different costs, and these costs can occur at significantly different times relative to when the power is used. The costs include the initial capital, and the costs of continuous operation, fuel, and maintenance as well as the costs of de-commissioning and remediating any environmental damage. Calculations of these costs can be made at the point of connection to a load or to the electricity grid, so that they may or may not include the transmission costs.
For comparing different methods, it is useful to compare costs per unit of energy which is typically given per kilowatt-hour or megawatt-hour. This type of calculation assists policymakers, researchers and others to guide discussions and decision making but is usually complicated by the need to take account of differences in timing by means of a discount rate. The consensus of recent major global studies of generation costs is that wind and solar power are the lowest-cost sources of electricity available today.
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- "Wikipedia: Cost of Electricity by Source" | 2021-10-12 | 11 Upvotes 1 Comments
π Gibbs Phenomenon
In mathematics, the Gibbs phenomenon, discovered by Henry WilbrahamΒ (1848) and rediscovered by J. Willard GibbsΒ (1899), is the peculiar manner in which the Fourier series of a piecewise continuously differentiable periodic function behaves at a jump discontinuity. The nth partial sum of the Fourier series has large oscillations near the jump, which might increase the maximum of the partial sum above that of the function itself. The overshoot does not die out as n increases, but approaches a finite limit. This sort of behavior was also observed by experimental physicists, but was believed to be due to imperfections in the measuring apparatus.
This is one cause of ringing artifacts in signal processing.
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- "Gibbs Phenomenon" | 2021-06-01 | 40 Upvotes 27 Comments
π Battle Chess
Battle Chess is a computer game version of chess in which the chess pieces come to life and battle one another when capturing. It was originally developed and released by Interplay Entertainment for the Amiga in 1988 and subsequently on many other systems, including 3DO Interactive Multiplayer, Acorn Archimedes, Amiga CD32, Amiga CDTV, Apple IIGS, Apple IIe, Atari ST, Commodore 64, MS-DOS, FM Towns, NES, Mac OS, NEC PC-9801, X68000 and Microsoft Windows. In 1991, Battle Chess Enhanced was released by Interplay for the PC, featuring improved VGA graphics and a symphonic musical score that played from the CD-ROM.
Battle Chess was critically acclaimed and commercially successful, resulting in two official follow-ups as well as several inspired games. Its remake, Battle Chess: Game of Kings, was released on Steam on December 11, 2015.
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- "Battle Chess" | 2019-11-24 | 132 Upvotes 90 Comments
π 4X
4X is a genre of strategy-based video and board games in which players control an empire and "eXplore, eXpand, eXploit, and eXterminate". The term was coined by Alan Emrich in his September 1993 preview of Master of Orion for Computer Gaming World. Since then, others have adopted the term to describe games of similar scope and design.
4X computer games are noted for their deep, complex gameplay. Emphasis is placed upon economic and technological development, as well as a range of non-military routes to supremacy. Games can take a long time to complete since the amount of micromanagement needed to sustain an empire increases as the empire grows. 4X games are sometimes criticized for becoming tedious for these reasons, and several games have attempted to address these concerns by limiting micromanagement, with varying degrees of success.
The earliest 4X games borrowed ideas from board games and 1970s text-based computer games. The first 4X computer games were turn-based, but real-time 4X games are not uncommon. Many 4X computer games were published in the mid-1990s, but were later outsold by other types of strategy games. Sid Meier's Civilization is an important example from this formative era, and popularized the level of detail that later became a staple of the genre. In the new millennium, several 4X releases have become critically and commercially successful.
In the board (and card) game domain, 4X is less of a distinct genre, in part because of the practical constraints of components and playing time. The Civilization board game that gave rise to Sid Meier's Civilization computer game, for instance, has no exploration and no extermination. Unless extermination is targeted at non-player entities, it tends to be either nearly impossible (because of play balance mechanisms, since player elimination is usually considered an undesirable feature) or certainly unachievable (because victory conditions are triggered before extermination can be completed) in board games.
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- "4X" | 2019-02-03 | 124 Upvotes 25 Comments
π Constraint Logic Programming
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.
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- "Constraint Logic Programming" | 2022-04-11 | 21 Upvotes 3 Comments