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πŸ”— Stanford Bunny

πŸ”— Computing πŸ”— Computer graphics

The Stanford bunny is a computer graphics 3D test model developed by Greg Turk and Marc Levoy in 1994 at Stanford University. The model consists of 69,451 triangles, with the data determined by 3D scanning a ceramic figurine of a rabbit. This figurine and others were scanned to test methods of range scanning physical objects.

The data can be used to test various graphics algorithms, including polygonal simplification, compression, and surface smoothing. There are a few complications with this dataset that can occur in any 3D scan data: the model is manifold connected and has holes in the data, some due to scanning limits and some due to the object being hollow. These complications provide a more realistic input for any algorithm that is benchmarked with the Stanford bunny, though by today's standards, in terms of geometric complexity and triangle count, it is considered a simple model.

The model was originally available in .ply (polygons) file format with 4 different resolutions.

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πŸ”— Curry's paradox: "If this sentence is true, then Santa Claus exists."

πŸ”— Mathematics

Curry's paradox is a paradox in which an arbitrary claim F is proved from the mere existence of a sentence C that says of itself "If C, then F", requiring only a few apparently innocuous logical deduction rules. Since F is arbitrary, any logic having these rules proves everything. The paradox may be expressed in natural language and in various logics, including certain forms of set theory, lambda calculus, and combinatory logic.

The paradox is named after the logician Haskell Curry. It has also been called LΓΆb's paradox after Martin Hugo LΓΆb, due to its relationship to LΓΆb's theorem.

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πŸ”— John Titor

πŸ”— Internet culture πŸ”— Skepticism πŸ”— Alternative Views πŸ”— Paranormal

John Titor (May 5, 6 or 7, 1998) is a name used on several bulletin boards during 2000 and 2001 by a poster claiming to be an American military time traveler from 2036. Titor made numerous vague and specific predictions regarding calamitous events in 2004 and beyond, including a nuclear war, none of which came true. Subsequent closer examination of Titor's assertions provoked widespread skepticism. Inconsistencies in his explanations, the uniform inaccuracy of his predictions, and a private investigator's findings all led to the general impression that the entire episode was an elaborate hoax. A 2009 investigation concluded that Titor was likely the creation of Larry Haber, a Florida entertainment lawyer, along with his brother Morey, a computer scientist.

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πŸ”— Canon Cat

πŸ”— Computing

The Canon Cat was a task-dedicated, desktop computer released by Canon Inc. in 1987 at a price of US$1,495. On the surface it was not unlike the dedicated word processors popular in the late 1970s to early 1980s, but it was far more powerful and incorporated many unique ideas for data manipulation.

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πŸ”— Jaccard Index

πŸ”— Computer science πŸ”— Statistics

The Jaccard index, also known as the Jaccard similarity coefficient, is a statistic used for gauging the similarity and diversity of sample sets. It was developed by Grove Karl Gilbert in 1884 as his ratio of verification (v) and now is frequently referred to as the Critical Success Index in meteorology. It was later developed independently by Paul Jaccard, originally giving the French name coefficient de communautΓ©, and independently formulated again by T. Tanimoto. Thus, the Tanimoto index or Tanimoto coefficient are also used in some fields. However, they are identical in generally taking the ratio of Intersection over Union. The Jaccard coefficient measures similarity between finite sample sets, and is defined as the size of the intersection divided by the size of the union of the sample sets:

J ( A , B ) = | A ∩ B | | A βˆͺ B | = | A ∩ B | | A | + | B | βˆ’ | A ∩ B | . {\displaystyle J(A,B)={{|A\cap B|} \over {|A\cup B|}}={{|A\cap B|} \over {|A|+|B|-|A\cap B|}}.}

Note that by design, 0 ≀ J ( A , B ) ≀ 1. {\displaystyle 0\leq J(A,B)\leq 1.} If A intersection B is empty, then J(A,B)Β =Β 0. The Jaccard coefficient is widely used in computer science, ecology, genomics, and other sciences, where binary or binarized data are used. Both the exact solution and approximation methods are available for hypothesis testing with the Jaccard coefficient.

Jaccard similarity also applies to bags, i.e., Multisets. This has a similar formula, but the symbols mean bag intersection and bag sum (not union). The maximum value is 1/2.

J ( A , B ) = | A ∩ B | | A ⊎ B | = | A ∩ B | | A | + | B | . {\displaystyle J(A,B)={{|A\cap B|} \over {|A\uplus B|}}={{|A\cap B|} \over {|A|+|B|}}.}

The Jaccard distance, which measures dissimilarity between sample sets, is complementary to the Jaccard coefficient and is obtained by subtracting the Jaccard coefficient from 1, or, equivalently, by dividing the difference of the sizes of the union and the intersection of two sets by the size of the union:

d J ( A , B ) = 1 βˆ’ J ( A , B ) = | A βˆͺ B | βˆ’ | A ∩ B | | A βˆͺ B | . {\displaystyle d_{J}(A,B)=1-J(A,B)={{|A\cup B|-|A\cap B|} \over |A\cup B|}.}

An alternative interpretation of the Jaccard distance is as the ratio of the size of the symmetric difference A β–³ B = ( A βˆͺ B ) βˆ’ ( A ∩ B ) {\displaystyle A\triangle B=(A\cup B)-(A\cap B)} to the union. Jaccard distance is commonly used to calculate an n Γ— n matrix for clustering and multidimensional scaling of n sample sets.

This distance is a metric on the collection of all finite sets.

There is also a version of the Jaccard distance for measures, including probability measures. If ΞΌ {\displaystyle \mu } is a measure on a measurable space X {\displaystyle X} , then we define the Jaccard coefficient by

J ΞΌ ( A , B ) = ΞΌ ( A ∩ B ) ΞΌ ( A βˆͺ B ) , {\displaystyle J_{\mu }(A,B)={{\mu (A\cap B)} \over {\mu (A\cup B)}},}

and the Jaccard distance by

d ΞΌ ( A , B ) = 1 βˆ’ J ΞΌ ( A , B ) = ΞΌ ( A β–³ B ) ΞΌ ( A βˆͺ B ) . {\displaystyle d_{\mu }(A,B)=1-J_{\mu }(A,B)={{\mu (A\triangle B)} \over {\mu (A\cup B)}}.}

Care must be taken if ΞΌ ( A βˆͺ B ) = 0 {\displaystyle \mu (A\cup B)=0} or ∞ {\displaystyle \infty } , since these formulas are not well defined in these cases.

The MinHash min-wise independent permutations locality sensitive hashing scheme may be used to efficiently compute an accurate estimate of the Jaccard similarity coefficient of pairs of sets, where each set is represented by a constant-sized signature derived from the minimum values of a hash function.

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πŸ”— Alcubierre drive

πŸ”— Spaceflight πŸ”— Physics πŸ”— Alternative Views πŸ”— Physics/relativity

The Alcubierre drive, Alcubierre warp drive, or Alcubierre metric (referring to metric tensor) is a speculative idea based on a solution of Einstein's field equations in general relativity as proposed by Mexican theoretical physicist Miguel Alcubierre, by which a spacecraft could achieve apparent faster-than-light travel if a configurable energy-density field lower than that of vacuum (that is, negative mass) could be created.

Rather than exceeding the speed of light within a local reference frame, a spacecraft would traverse distances by contracting space in front of it and expanding space behind it, resulting in effective faster-than-light travel. Objects cannot accelerate to the speed of light within normal spacetime; instead, the Alcubierre drive shifts space around an object so that the object would arrive at its destination faster than light would in normal space without breaking any physical laws.

Although the metric proposed by Alcubierre is consistent with the Einstein field equations, construction of such a drive is not necessarily possible. The proposed mechanism of the Alcubierre drive implies a negative energy density and therefore requires exotic matter. So if exotic matter with the correct properties cannot exist, then the drive could not be constructed. At the close of his original article, however, Alcubierre argued (following an argument developed by physicists analyzing traversable wormholes) that the Casimir vacuum between parallel plates could fulfill the negative-energy requirement for the Alcubierre drive.

Another possible issue is that, although the Alcubierre metric is consistent with Einstein's equations, general relativity does not incorporate quantum mechanics. Some physicists have presented arguments to suggest that a theory of quantum gravity (which would incorporate both theories) would eliminate those solutions in general relativity that allow for backwards time travel (see the chronology protection conjecture) and thus make the Alcubierre drive invalid.

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πŸ”— Soundex – a phonetic algorithm for indexing names by sound

πŸ”— Computer science πŸ”— Linguistics πŸ”— Linguistics/Applied Linguistics

Soundex is a phonetic algorithm for indexing names by sound, as pronounced in English. The goal is for homophones to be encoded to the same representation so that they can be matched despite minor differences in spelling. The algorithm mainly encodes consonants; a vowel will not be encoded unless it is the first letter. Soundex is the most widely known of all phonetic algorithms (in part because it is a standard feature of popular database software such as DB2, PostgreSQL, MySQL, SQLite, Ingres, MS SQL Server and Oracle.) Improvements to Soundex are the basis for many modern phonetic algorithms.

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πŸ”— B.a.t.m.a.n

πŸ”— Telecommunications

The Better Approach to Mobile Ad-hoc Networking (B.A.T.M.A.N.) is a routing protocol for multi-hop mobile ad hoc networks which is under development by the German "Freifunk" community and intended to replace the Optimized Link State Routing Protocol (OLSR).

B.A.T.M.A.N.'s crucial point is the decentralization of knowledge about the best route through the networkΒ β€” no single node has all the data. This technique eliminates the need to spread information about network changes to every node in the network. The individual node only saves information about the "direction" it received data from and sends its data accordingly. The data gets passed from node to node, and packets get individual, dynamically created routes. A network of collective intelligence is created.

In early 2007, the B.A.T.M.A.N. developers started experimenting with the idea of routing on layer 2 (Ethernet layer) instead of layer 3. To differentiate from the layer 3 routing daemon, the suffix "adv" (for: advanced) was chosen. Instead of manipulating routing tables based on information exchanged via UDP/IP, it provides a virtual network interface and transparently transports Ethernet packets on its own. The batman-adv kernel module has been part of the official Linux kernel since 2.6.38.

πŸ”— Elder Mother

πŸ”— Denmark πŸ”— Folklore

The Elder Mother is an elder-guarding being in English and Scandinavian folklore known by a variety of names, such as the Danish Hyldemoer ("Elder-Mother") and the Lincolnshire names Old Lady and Old Girl.

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πŸ”— Wife Acceptance Factor

πŸ”— Psychology πŸ”— Gender Studies

Wife acceptance factor, wife approval factor, or wife appeal factor (WAF) is an assessment of design elements that either increase or diminish the likelihood a wife will approve the purchase of expensive consumer electronics products such as high-fidelity loudspeakers, home theater systems and personal computers. Stylish, compact forms and appealing colors are commonly considered to have a high WAF. The term is a tongue-in-cheek play on electronics jargon such as "form factor" and "power factor" and derives from the idea that men are predisposed to appreciate gadgetry and performance criteria whereas women must be wooed by visual and aesthetic factors.

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