Random Articles (Page 2)
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π Autostereogram
An autostereogram is a single-image stereogram (SIS), designed to create the visual illusion of a three-dimensional (3D) scene from a two-dimensional image. In order to perceive 3D shapes in these autostereograms, one must overcome the normally automatic coordination between accommodation (focus) and horizontal vergence (angle of one's eyes). The illusion is one of depth perception and involves stereopsis: depth perception arising from the different perspective each eye has of a three-dimensional scene, called binocular parallax.
The simplest type of autostereogram consists of horizontally repeating patterns (often separate images) and is known as a wallpaper autostereogram. When viewed with proper convergence, the repeating patterns appear to float above or below the background. The well-known Magic Eye books feature another type of autostereogram called a random dot autostereogram. One such autostereogram is illustrated above right. In this type of autostereogram, every pixel in the image is computed from a pattern strip and a depth map. A hidden 3D scene emerges when the image is viewed with the correct convergence.
Autostereograms are similar to normal stereograms except they are viewed without a stereoscope. A stereoscope presents 2D images of the same object from slightly different angles to the left eye and the right eye, allowing us to reconstruct the original object via binocular disparity. When viewed with the proper vergence, an autostereogram does the same, the binocular disparity existing in adjacent parts of the repeating 2D patterns.
There are two ways an autostereogram can be viewed: wall-eyed and cross-eyed. Most autostereograms (including those in this article) are designed to be viewed in only one way, which is usually wall-eyed. Wall-eyed viewing requires that the two eyes adopt a relatively parallel angle, while cross-eyed viewing requires a relatively convergent angle. An image designed for wall-eyed viewing if viewed correctly will appear to pop out of the background, while if viewed cross-eyed it will instead appear as a cut-out behind the background and may be difficult to bring entirely into focus.
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- "Autostereogram" | 2020-01-13 | 17 Upvotes 4 Comments
π Cryotron
The cryotron is a switch that operates using superconductivity. The cryotron works on the principle that magnetic fields destroy superconductivity. This simple device consists of two superconducting wires (e.g. tantalum and niobium) with different critical temperature (Tc). The cryotron was invented by Dudley Allen Buck of the Massachusetts Institute of Technology Lincoln Laboratory.
As described by Buck, a straight wire of tantalum (having lower Tc) is wrapped around with a wire of niobium in a single layer coil. Both wires are electrically isolated from each other. When this device is immersed in a liquid helium bath both wires become superconducting and hence offer no resistance to the passage of electric current. Tantalum in superconducting state can carry large amount of current as compared to its normal state. Now when current is passed through the niobium coil (wrapped around tantalum) it produces a magnetic field, which in turn reduces (kills) the superconductivity of the tantalum wire and hence reduces the amount of the current that can flow through the tantalum wire. Hence one can control the amount of the current that can flow in the straight wire with the help of small current in the coiled wire. We can think of the tantalum straight wire as a "gate" and the coiled niobium as a "control".
The article by Buck includes descriptions of several logic circuits implemented using cryotrons, including: one stage of a binary adder, carry network, binary accumulator stage, and two stages of a cryotron stepping register.
A planar cryotron using thin films of lead and tin was developed in 1957 by John Bremer at General Electric's General Engineering Lab in Schenectady, New York. This was one of the first integrated circuits, although using superconductors rather than semiconductors. In the next few years, a demonstration computer was made and arrays with 2000 devices operated. A short history of this work is in the November 2007 newsletter of the IEEE History Center.
Juri Matisoo developed a version of the cryotron incorporating a Josephson junction switched by the magnetic field from a control wire. He also explained the shortcomings of traditional cryotrons in which the superconductive material must transition between superconducting and normal states to switch the device, and thus switch relatively slowly. Matisoo's cryotron switched between a conducting state in which 'pair tunneling' of electrons through the gate took place and a 'resistive' state where only single electrons were able to tunnel. The circuit was (like the traditional cryotron) capable of some amplification (i.e gain greater than unity) had a switching rate of less than 800 picoseconds. Although the requirement for cryogenic cooling limited its practicality, it wasn't until the late 2010s that commercial transistors came close to matching this performance.
There have been periods of renewed interest in various types of cryotron, IBM experimented with using them for limited applications in supercomputers during the 1980s and (as of 2020) there has been some investigation of their potential applications both to I/O and logic in prototype quantum computers.
π List of people and companies named in the Paradise Papers
This is a list of people and organisations named in the Paradise Papers as connected to offshore companies. The International Consortium of Investigative Journalists stated in their politicians database, as a disclaimer, "There are legitimate uses for offshore companies and trusts. We do not intend to suggest or imply that any people, companies or other entities included in the ICIJ Offshore Leaks Database have broken the law or otherwise acted improperly."
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- "List of people and companies named in the Paradise Papers" | 2017-11-06 | 36 Upvotes 1 Comments
π Pierre Menard, Author of the Quixote
"Pierre Menard, Author of the Quixote" (original Spanish title: "Pierre Menard, autor del Quijote") is a short story by Argentine writer Jorge Luis Borges.
It originally appeared in Spanish in the Argentine journal Sur in May 1939. The Spanish-language original was first published in book form in Borges's 1941 collection El jardΓn de senderos que se bifurcan (The Garden of Forking Paths), which was included in his much-reprinted Ficciones (1944).
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- "Pierre Menard, Author of the Quixote" | 2023-06-01 | 56 Upvotes 26 Comments
π Method of loci
The method of loci (loci being Latin for "places") is a strategy of memory enhancement which uses visualizations of familiar spatial environments in order to enhance the recall of information. The method of loci is also known as the memory journey, memory palace, or mind palace technique. This method is a mnemonic device adopted in ancient Roman and Greek rhetorical treatises (in the anonymous Rhetorica ad Herennium, Cicero's De Oratore, and Quintilian's Institutio Oratoria). Many memory contest champions report using this technique to recall faces, digits, and lists of words.
The term is most often found in specialised works on psychology, neurobiology, and memory, though it was used in the same general way at least as early as the first half of the nineteenth century in works on rhetoric, logic, and philosophy. John O'Keefe and Lynn Nadel refer to:
'the method of loci', an imaginal technique known to the ancient Greeks and Romans and described by Yates (1966) in her book The Art of Memory as well as by Luria (1969). In this technique the subject memorizes the layout of some building, or the arrangement of shops on a street, or any geographical entity which is composed of a number of discrete loci. When desiring to remember a set of items the subject 'walks' through these loci in their imagination and commits an item to each one by forming an image between the item and any feature of that locus. Retrieval of items is achieved by 'walking' through the loci, allowing the latter to activate the desired items. The efficacy of this technique has been well established (Ross and Lawrence 1968, Crovitz 1969, 1971, Briggs, Hawkins and Crovitz 1970, Lea 1975), as is the minimal interference seen with its use.
The items to be remembered in this mnemonic system are mentally associated with specific physical locations. The method relies on memorized spatial relationships to establish order and recollect memorial content. It is also known as the "Journey Method", used for storing lists of related items, or the "Roman Room" technique, which is most effective for storing unrelated information.
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- "Method of loci" | 2015-10-12 | 49 Upvotes 34 Comments
π Tsundoku
Tsundoku (Japanese: η©γθͺ) is acquiring reading materials but letting them pile up in one's home without reading them.
The term originated in the Meiji era (1868β1912) as Japanese slang. It combines elements of tsunde-oku (η©γγ§γγ, to pile things up ready for later and leave) and dokusho (θͺζΈ, reading books). It is also used to refer to books ready for reading later when they are on a bookshelf. As currently written, the word combines the characters for "pile up" (η©) and the character for "read" (θͺ).
The American author and bibliophile A. Edward Newton commented on a similar state.
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- "Tsundoku β Phenomenon of acquiring reading materials but letting them pile up" | 2023-10-16 | 43 Upvotes 14 Comments
- "Tsundoku" | 2020-02-12 | 58 Upvotes 48 Comments
π List of things named after Carl Friedrich Gauss
Carl Friedrich Gauss (1777β1855) is the eponym of all of the topics listed below. There are over 100 topics all named after this German mathematician and scientist, all in the fields of mathematics, physics, and astronomy. The English eponymous adjective Gaussian is pronounced GOWSS-ee-Ιn.
π Winnie-the-Pooh (Book)
Winnie-the-Pooh (1926) is the first volume of stories about Winnie-the-Pooh, written by A. A. Milne and illustrated by E. H. Shepard. The book focuses on the adventures of a teddy bear called Winnie-the-Pooh and his friends Piglet, a small toy pig; Eeyore, a toy donkey; Owl, a live owl; and Rabbit, a live rabbit. The characters of Kanga, a toy kangaroo, and her son Roo are introduced later in the book, in the chapter entitled "In Which Kanga and Baby Roo Come to the Forest and Piglet has a Bath". The bouncy toy-tiger character of Tigger is not introduced until the sequel, The House at Pooh Corner.
In 2003, Winnie the Pooh was listed at number 7 on the BBC's survey The Big Read.
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- "Winnie-the-Pooh (Book)" | 2019-10-14 | 13 Upvotes 5 Comments
π Greater Fool Theory
In finance, the greater fool theory suggests that one can sometimes make money through the purchase of overvalued assetsβββitems with a purchase price drastically exceeding the intrinsic valueβββif those assets can later be resold at an even higher price.
In this context, one "fool" might pay for an overpriced asset, on the assumption that he can probably sell it to an even "greater fool" and make a profit. This only works as long as there are new "greater fools" willing to pay higher and higher prices for the asset. Eventually, investors can no longer deny that the price is out of touch with reality, at which point a sell-off can cause the price to drop significantly until it is closer to its fair value.
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- "Greater Fool Theory" | 2022-01-30 | 12 Upvotes 2 Comments
π Chloropicrin
Chloropicrin, also known as PS and nitrochloroform, is a chemical compound currently used as a broad-spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide. It was used as a poison gas in World War I. Its chemical structural formula is Cl3CNO2.
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- "Chloropicrin" | 2023-08-08 | 11 Upvotes 1 Comments