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πŸ”— Citicorp Center Engineering Crisis

πŸ”— New York City πŸ”— Engineering

The Citicorp Center engineering crisis was the discovery, in 1978, of a significant structural flaw in Citicorp Center, then a recently completed skyscraper in New York City, and the subsequent effort to quietly make repairs over the next few months. The building, now known as Citigroup Center, occupied an entire block and was to be the headquarters of Citibank. Its structure, designed by William LeMessurier, had several unusual design features, including a raised base supported by four offset stilts, and diagonal bracing which absorbed wind loads from upper stories.

In the original design, potential wind loads for the building were calculated incorrectly. The flaw was discovered by Diane Hartley, an undergraduate student at Princeton University who was writing a thesis on the building, and was communicated to the firm responsible for the structural design. LeMessurier was subsequently lauded for acknowledging his error and orchestrating a successful repair effort. Estimates at the time suggested that the building could be toppled by a 70-mile-per-hour (110Β km/h) wind, with possibly many people killed as a result. The crisis was kept secret until 1995 and Hartley had no knowledge of the significance of her work until after that time.

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πŸ”— Quiescence search

πŸ”— Chess

Quiescence search is an algorithm typically used to extend search at unstable nodes in minimax game trees in game-playing computer programs. It is an extension of the evaluation function to defer evaluation until the position is stable enough to be evaluated statically, that is, without considering the history of the position or future moves from the position. It mitigates the effect of the horizon problem faced by AI engines for various games like chess and Go.

Human players usually have enough intuition to decide whether to abandon a bad-looking move, or search a promising move to a great depth. A quiescence search attempts to emulate this behavior by instructing a computer to search "volatile" positions to a greater depth than "quiet" ones to make sure there are no hidden traps and to get a better estimate of its value.

Any sensible criterion may be used to distinguish "quiet" positions from "volatile" positions. One common criterion is that moves exist in the position that can dramatically change the valuation of the position, such as captures in chess or Go. As the main motive of quiescence search is to get a stable value out of a static evaluation function, it may also make sense to detect wide fluctuations in values returned by a simple heuristic evaluator over several ply, i.e. a history criterion. The quiescence search continues as along as the position remains volatile according to the criterion. In order to get the quiescence search to terminate, plies are usually restricted to moves that deal directly with the threat, such as moves that capture and recapture (often called a 'capture search') in chess. In highly "unstable" games like Go and reversi, a rather large proportion of computer time may be spent on quiescence searching.

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πŸ”— Reverse graffiti

πŸ”— Marketing & Advertising πŸ”— Brands πŸ”— Graffiti

Reverse graffiti is a method of creating temporary or semi-permanent images on walls or other surfaces by removing dirt from a surface. It can also be done by simply removing dirt with the fingertip from windows or other dirty surfaces, such as writing "wash me" on a dirty vehicle. Others, such as graffiti artist Moose, use a cloth or a high-power washer to remove dirt on a larger scale.

Reverse graffiti has been used as a form of advertising, although this usage has been controversial, as its legality varies depending on jurisdiction.

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πŸ”— Miller Columns

πŸ”— Apple Inc./Macintosh πŸ”— Apple Inc.

Miller columns (also known as cascading lists) are a browsing/visualization technique that can be applied to tree structures. The columns allow multiple levels of the hierarchy to be open at once, and provide a visual representation of the current location. It is closely related to techniques used earlier in the Smalltalk browser, but was independently invented by Mark S. Miller in 1980 at Yale University. The technique was then used at Project Xanadu, Datapoint, and NeXT.

While at Datapoint, Miller generalized the technique to browse directed graphs with labeled nodes and arcs. In all cases, the technique is appropriate for structures with high degree (large fanout). For low-degree structures, outline editors or graph viewers are more effective.

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πŸ”— VRML – Virtual Reality Markup Language

πŸ”— Computing πŸ”— Computing/Software πŸ”— Computing/Websites

VRML (Virtual Reality Modeling Language, pronounced vermal or by its initials, originallyβ€”before 1995β€”known as the Virtual Reality Markup Language) is a standard file format for representing 3-dimensional (3D) interactive vector graphics, designed particularly with the World Wide Web in mind. It has been superseded by X3D.

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πŸ”— Wringing

πŸ”— Technology πŸ”— Sweden πŸ”— Metalworking

Gauge blocks (also known as gage blocks, Johansson gauges, slip gauges, or Jo blocks) are a system for producing precision lengths. The individual gauge block is a metal or ceramic block that has been precision ground and lapped to a specific thickness. Gauge blocks come in sets of blocks with a range of standard lengths. In use, the blocks are stacked to make up a desired length.

An important feature of gauge blocks is that they can be joined together with very little dimensional uncertainty. The blocks are joined by a sliding process called wringing, which causes their ultra-flat surfaces to cling together. A small number of gauge blocks can be used to create accurate lengths within a wide range. By using 3 blocks at a time taken from a set of 30 blocks, one may create any of the 1000 lengths from 3.000 to 3.999Β mm in 0.001Β mm steps (or .3000 to .3999 inches in 0.0001Β inch steps). Gauge blocks were invented in 1896 by Swedish machinist Carl Edvard Johansson. They are used as a reference for the calibration of measuring equipment used in machine shops, such as micrometers, sine bars, calipers, and dial indicators (when used in an inspection role). Gauge blocks are the main means of length standardization used by industry.

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πŸ”— Xenobot

πŸ”— Biology πŸ”— Engineering πŸ”— Science

Xenobots, named after the African clawed frog (Xenopus laevis), are synthetic organisms that are automatically designed by computers to perform some desired function and built by combining together different biological tissues.

Xenobots are less than a 1 millimeter (0.039 inches) wide and composed of just two things: skin cells and heart muscle cells, both of which are derived from stem cells harvested from early (blastula stage) frog embryos. The skin cells provide rigid support and the heart cells act as small motors, contracting and expanding in volume to propel the xenobot forward. The shape of a xenobot's body, and its distribution of skin and heart cells, are automatically designed in simulation to perform a specific task, using a process of trial and error (an evolutionary algorithm). Xenobots have been designed to walk, swim, push pellets, carry payloads, and work together in a swarm to aggregate debris scattered along the surface of their dish into neat piles. They can survive for weeks without food and heal themselves after lacerations.

πŸ”— Toxic squash syndrome

πŸ”— Chemicals πŸ”— Plants

Cucurbitacin is a class of biochemical compounds that some plants – notably members of the pumpkin and gourd family, Cucurbitaceae – produce and which function as a defence against herbivores. Cucurbitacins are chemically classified as triterpenes, formally derived from cucurbitane, a triterpene hydrocarbon – specifically, from the unsaturated variant cucurbit-5-ene, or 19(10β†’9Ξ²)-abeo-10Ξ±-lanost-5-ene. They often occur as glycosides. They and their derivatives have been found in many plant families (including Brassicaceae, Cucurbitaceae, Scrophulariaceae, Begoniaceae, Elaeocarpaceae, Datiscaceae, Desfontainiaceae, Polemoniaceae, Primulaceae, Rubiaceae, Sterculiaceae, Rosaceae, and Thymelaeaceae), in some mushrooms (including Russula and Hebeloma) and even in some marine mollusks.

Cucurbitacins may be a taste deterrent in plants foraged by some animals and in some edible plants preferred by humans, like cucumbers and zucchinis. In laboratory research, cucurbitacins have cytotoxic properties and are under study for their potential biological activities.

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πŸ”— Benford's Law: Fraud Detection

πŸ”— Mathematics πŸ”— Statistics

Benford's law, also called the Newcomb–Benford law, the law of anomalous numbers, or the first-digit law, is an observation about the frequency distribution of leading digits in many real-life sets of numerical data. The law states that in many naturally occurring collections of numbers, the leading digit is likely to be small. For example, in sets that obey the law, the number 1 appears as the leading significant digit about 30% of the time, while 9 appears as the leading significant digit less than 5% of the time. If the digits were distributed uniformly, they would each occur about 11.1% of the time. Benford's law also makes predictions about the distribution of second digits, third digits, digit combinations, and so on.

The graph to the right shows Benford's law for base 10, one of infinitely many cases of a generalized law regarding numbers expressed in arbitrary (integer) bases, which rules out the possibility that the phenomenon might be an artifact of the base 10 number system. Further generalizations were published by Hill in 1995 including analogous statements for both the nth leading digit as well as the joint distribution of the leading n digits, the latter of which leads to a corollary wherein the significant digits are shown to be a statistically dependent quantity. ).

It has been shown that this result applies to a wide variety of data sets, including electricity bills, street addresses, stock prices, house prices, population numbers, death rates, lengths of rivers, and physical and mathematical constants. Like other general principles about natural dataβ€”for example the fact that many data sets are well approximated by a normal distributionβ€”there are illustrative examples and explanations that cover many of the cases where Benford's law applies, though there are many other cases where Benford's law applies that resist a simple explanation. It tends to be most accurate when values are distributed across multiple orders of magnitude, especially if the process generating the numbers is described by a power law (which are common in nature).

The law is named after physicist Frank Benford, who stated it in 1938 in a paper titled "The Law of Anomalous Numbers", although it had been previously stated by Simon Newcomb in 1881.

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πŸ”— Domain tasting

πŸ”— Internet πŸ”— Marketing & Advertising

Domain tasting is the practice of temporarily registering a domain under the five-day Add Grace Period at the beginning of the registration of an ICANN-regulated second-level domain. During this period, a registration must be fully refunded by the domain name registry if cancelled. This was designed to address accidental registrations, but domain tasters use the Add Grace Period for illegal purposes.

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