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π Capacitor plague β Wikipedia
The capacitor plague was a problem related to a higher-than-expected failure rate of non-solid aluminum electrolytic capacitors, between 1999 and 2007, especially those from some Taiwanese manufacturers, due to faulty electrolyte composition that caused corrosion accompanied by gas generation, often rupturing the case of the capacitor from the build-up of pressure.
High failure rates occurred in many well-known brands of electronics, and were particularly evident in motherboards, video cards, and power supplies of personal computers.
Discussed on
- "Capacitor plague β Wikipedia" | 2017-11-05 | 65 Upvotes 36 Comments
- "Capacitor plague" | 2013-05-17 | 138 Upvotes 62 Comments
π 60163 Tornado, the first new build British mainline steam locomotive since 1960
LNER Peppercorn Class A1 No. 60163 Tornado is a 4-6-2 steam locomotive completed in 2008 to an original design by Arthur Peppercorn. It is the first new build British mainline steam locomotive since 1960, and the only Peppercorn Class A1 in existence after the original batch were scrapped. In 2017, Tornado became the first steam locomotive to officially reach 100Β mph (160Β km/h) on British tracks in over 50 years.
After the project was founded by the A1 Steam Locomotive Trust in 1990, construction of Tornado began in 1994 and mostly took place at Darlington Works, with other components manufactured elsewhere. The project was financed through fundraising initiatives, public donations, sponsorship deals, and hiring out Tornado itself for special services. The locomotive was granted its mainline certificate in January 2009, having been designed in compliance with modern safety and certification standards. Tornado has worked on heritage and mainline trains across Britain since 2008. In 2022, it was withdrawn for overhaul.
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- "60163 Tornado, the first new build British mainline steam locomotive since 1960" | 2023-03-13 | 102 Upvotes 68 Comments
π Shoelace formula
The shoelace formula or shoelace algorithm (also known as Gauss's area formula and the surveyor's formula) is a mathematical algorithm to determine the area of a simple polygon whose vertices are described by their Cartesian coordinates in the plane. The user cross-multiplies corresponding coordinates to find the area encompassing the polygon, and subtracts it from the surrounding polygon to find the area of the polygon within. It is called the shoelace formula because of the constant cross-multiplying for the coordinates making up the polygon, like tying shoelaces. It is also sometimes called the shoelace method. It has applications in surveying and forestry, among other areas.
The formula was described by Meister (1724β1788) in 1769 and by Gauss in 1795. It can be verified by dividing the polygon into triangles, and can be considered to be a special case of Green's theorem.
The area formula is derived by taking each edge AB, and calculating the area of triangle ABO with a vertex at the origin O, by taking the cross-product (which gives the area of a parallelogram) and dividing by 2. As one wraps around the polygon, these triangles with positive and negative area will overlap, and the areas between the origin and the polygon will be cancelled out and sum to 0, while only the area inside the reference triangle remains. This is why the formula is called the surveyor's formula, since the "surveyor" is at the origin; if going counterclockwise, positive area is added when going from left to right and negative area is added when going from right to left, from the perspective of the origin.
The area formula can also be applied to self-overlapping polygons since the meaning of area is still clear even though self-overlapping polygons are not generally simple. Furthermore, a self-overlapping polygon can have multiple "interpretations" but the Shoelace formula can be used to show that the polygon's area is the same regardless of the interpretation.
Discussed on
- "Shoelace formula" | 2018-12-02 | 73 Upvotes 12 Comments
- "Shoelace Formula" | 2014-12-26 | 27 Upvotes 3 Comments
π 1 + 2 + 3 + .. = -1/12
Ramanujan summation is a technique invented by the mathematician Srinivasa Ramanujan for assigning a value to divergent infinite series. Although the Ramanujan summation of a divergent series is not a sum in the traditional sense, it has properties which make it mathematically useful in the study of divergent infinite series, for which conventional summation is undefined.
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- "1 + 2 + 3 + .. = -1/12" | 2014-01-14 | 13 Upvotes 19 Comments
π Bleem
Bleem! (styled as bleem!) is a commercial PlayStation emulator released by the Bleem! Company in 1999 for IBM-compatible PCs and Dreamcast. It is notable for being one of the few commercial software emulators to be aggressively marketed during the emulated console's lifetime, and was the center of multiple controversial lawsuits.
Discussed on
- "Bleem" | 2024-03-08 | 13 Upvotes 1 Comments
π Ask HN: using only static magnetism - impossible to stably levitate against gravity?
Earnshaw's theorem states that a collection of point charges cannot be maintained in a stable stationary equilibrium configuration solely by the electrostatic interaction of the charges. This was first proven by British mathematician Samuel Earnshaw in 1842. It is usually referenced to magnetic fields, but was first applied to electrostatic fields.
Earnshaw's theorem applies to classical inverse-square law forces (electric and gravitational) and also to the magnetic forces of permanent magnets, if the magnets are hard (the magnets do not vary in strength with external fields). Earnshaw's theorem forbids magnetic levitation in many common situations.
If the materials are not hard, Braunbeck's extension shows that materials with relative magnetic permeability greater than one (paramagnetism) are further destabilising, but materials with a permeability less than one (diamagnetic materials) permit stable configurations.
Discussed on
- "Earnshaw's Theorem" | 2020-11-14 | 23 Upvotes 5 Comments
- "Ask HN: using only static magnetism - impossible to stably levitate against gravity?" | 2009-04-30 | 3 Upvotes 10 Comments
π Height in Sports
Height can significantly influence success in sports, depending on how the design of the sport is linked to factors that are height-biased due to physics and biology. The balance of the intricate array of links will determine the degree to which height plays a role in success, if any.
Discussed on
- "Height in Sports" | 2023-08-22 | 13 Upvotes 1 Comments
π Neutral Monism
Neutral monism is an umbrella term for a class of metaphysical theories in the philosophy of mind, concerning the relation of mind to matter. These theories take the fundamental nature of reality to be neither mental nor physical; in other words it is "neutral".
Neutral monism has gained prominence as a potential solution to theoretical issues within the philosophy of mind, specifically the mindβbody problem and the hard problem of consciousness. The mindβbody problem is the problem of explaining how mind relates to matter. The hard problem is a related philosophical problem targeted at physicalist theories of mind specifically: the problem arises because it is not obvious how a purely physical universe could give rise to conscious experience. This is because physical explanations are mechanistic: that is, they explain phenomena by appealing to underlying functions and structures. And, though explanations of this sort seem to work well for a wide variety of phenomena, conscious experience seems uniquely resistant to functional explanations. As the philosopher David Chalmers has put it: "even when we have explained the performance of all the cognitive and behavioral functions in the vicinity of experience - perceptual discrimination, categorization, internal access, verbal report - there may still remain a further unanswered question: Why is the performance of these functions accompanied by experience?" The hard problem has motivated Chalmers and other philosophers to abandon the project of explaining consciousness in terms physical or chemical mechanisms (only 56.5% of philosophers are physicalists, according to the most recent PhilPapers survey).
With this, there has been growing demand for alternative ontologies (such as neutral monism) that may provide explanatory frameworks more suitable for explaining the existence of consciousness. It has been accepted by several prominent English-speaking philosophers, such as William James and Bertrand Russell.
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- "Neutral Monism" | 2023-10-31 | 12 Upvotes 1 Comments
π 1808/1809 Mystery Eruption
The 1808 mystery eruption was a large volcanic eruption conjectured to have taken place in late 1808, possibly in the southwest Pacific. A VEI-6 eruption, comparable to the 1883 eruption of Krakatoa, is suspected of having contributed to a period of global cooling that lasted for years, analogous to how the 1815 eruption of Mount Tambora (VEI-7) led to the Year Without a Summer in 1816.
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- "1808/1809 Mystery Eruption" | 2019-06-09 | 60 Upvotes 9 Comments
π Circle-Ellipse Problem
The circleβellipse problem in software development (sometimes called the squareβrectangle problem) illustrates several pitfalls which can arise when using subtype polymorphism in object modelling. The issues are most commonly encountered when using object-oriented programming (OOP). By definition, this problem is a violation of the Liskov substitution principle, one of the SOLID principles.
The problem concerns which subtyping or inheritance relationship should exist between classes which represent circles and ellipses (or, similarly, squares and rectangles). More generally, the problem illustrates the difficulties which can occur when a base class contains methods which mutate an object in a manner which may invalidate a (stronger) invariant found in a derived class, causing the Liskov substitution principle to be violated.
The existence of the circleβellipse problem is sometimes used to criticize object-oriented programming. It may also imply that hierarchical taxonomies are difficult to make universal, implying that situational classification systems may be more practical.
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- "Circle-Ellipse Problem" | 2011-04-17 | 21 Upvotes 20 Comments