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🔗 Mathematics

The Karnaugh map (KM or K-map) is a method of simplifying Boolean algebra expressions. Maurice Karnaugh introduced it in 1953 as a refinement of Edward Veitch's 1952 Veitch chart, which actually was a rediscovery of Allan Marquand's 1881 logical diagram aka Marquand diagram but with a focus now set on its utility for switching circuits. Veitch charts are therefore also known as Marquand–Veitch diagrams, and Karnaugh maps as Karnaugh–Veitch maps (KV maps).

The Karnaugh map reduces the need for extensive calculations by taking advantage of humans' pattern-recognition capability. It also permits the rapid identification and elimination of potential race conditions.

The required Boolean results are transferred from a truth table onto a two-dimensional grid where, in Karnaugh maps, the cells are ordered in Gray code, and each cell position represents one combination of input conditions, while each cell value represents the corresponding output value. Optimal groups of 1s or 0s are identified, which represent the terms of a canonical form of the logic in the original truth table. These terms can be used to write a minimal Boolean expression representing the required logic.

Karnaugh maps are used to simplify real-world logic requirements so that they can be implemented using a minimum number of physical logic gates. A sum-of-products expression can always be implemented using AND gates feeding into an OR gate, and a product-of-sums expression leads to OR gates feeding an AND gate. Karnaugh maps can also be used to simplify logic expressions in software design. Boolean conditions, as used for example in conditional statements, can get very complicated, which makes the code difficult to read and to maintain. Once minimised, canonical sum-of-products and product-of-sums expressions can be implemented directly using AND and OR logic operators. Diagrammatic and mechanical methods for minimizing simple logic expressions have existed since at least the medieval times. More systematic methods for minimizing complex expressions began to be developed in the early 1950s, but until the mid to late 1980s the Karnaugh map was the most common used in practice.

🔗 Mathematics 🔗 Physics

A topological quantum computer is a theoretical quantum computer that employs two-dimensional quasiparticles called anyons, whose world lines pass around one another to form braids in a three-dimensional spacetime (i.e., one temporal plus two spatial dimensions). These braids form the logic gates that make up the computer. The advantage of a quantum computer based on quantum braids over using trapped quantum particles is that the former is much more stable. Small, cumulative perturbations can cause quantum states to decohere and introduce errors in the computation, but such small perturbations do not change the braids' topological properties. This is like the effort required to cut a string and reattach the ends to form a different braid, as opposed to a ball (representing an ordinary quantum particle in four-dimensional spacetime) bumping into a wall. Alexei Kitaev proposed topological quantum computation in 1997. While the elements of a topological quantum computer originate in a purely mathematical realm, experiments in fractional quantum Hall systems indicate these elements may be created in the real world using semiconductors made of gallium arsenide at a temperature of near absolute zero and subjected to strong magnetic fields.

🔗 Military history 🔗 China 🔗 Urban studies and planning 🔗 Military history/Fortifications 🔗 Military history/Asian military history 🔗 Hong Kong 🔗 Military history/Chinese military history 🔗 Organized crime

Kowloon Walled City was an ungoverned, densely populated settlement in Kowloon City, Hong Kong. Originally a Chinese military fort, the Walled City became an enclave after the New Territories were leased to the UK by China in 1898. Its population increased dramatically following the Japanese occupation of Hong Kong during World War II. By 1990, the walled city contained 50,000 residents within its 2.6-hectare (6.4-acre) borders. From the 1950s to the 1970s, it was controlled by local triads and had high rates of prostitution, gambling, and drug abuse.

In January 1987, the Hong Kong municipal government announced plans to demolish the walled city. After an arduous eviction process, demolition began in March 1993 and was completed in April 1994. Kowloon Walled City Park opened in December 1995 and occupies the area of the former Walled City. Some historical artefacts from the walled city, including its yamen building and remnants of its southern gate, have been preserved there.

🔗 United States 🔗 Film 🔗 Library of Congress 🔗 Film/American cinema 🔗 Film/Silent films 🔗 Film/Documentary films 🔗 United States/Film - American cinema

A Trip Down Market Street is a 13-minute actuality film recorded by placing a movie camera on the front of a cable car as it traveled down San Francisco’s Market Street. The film shows many details of daily life in a major early 20th century American city, including the transportation, fashions and architecture of the era. The film begins at 8th Street and continues eastward to the cable car turntable, at The Embarcadero, in front of the Ferry Building. Landmarks passed in the latter part of the first half include the Call Building (then San Francisco's tallest) and the Palace Hotel (both on the right; Lotta's Fountain is on the left between the two but is in the shade). The film was produced by the four Miles brothers: Harry, Herbert, Earle and Joe. It is notable for capturing San Francisco four days before the 1906 San Francisco earthquake, which started on the morning of Wednesday, April 18, 1906.

The Miles brothers had been producing films in New York including films shot in San Francisco. In September 1905 they shot the fight between Oscar "Battling" Nelson and Jimmy Britt in Colma, California, just south of San Francisco city limits. The Miles brothers established a studio at 1139 Market Street in San Francisco in early 1906. They shot a railroad descent down Mount Tamalpais as well as the Market Street film. On April 17, Harry and Joe Miles boarded a train for New York, taking the two films with them, but they heard about the earthquake and sent the films to New York while they boarded another train headed back to San Francisco. The Turk Street house of Earle Miles survived the earthquake and subsequent catastrophic fire but the studio did not. The Miles brothers based their business out of Earle's home, and shot more film of post-earthquake scenes; some of this footage, including that of a second trip down a now devastated Market Street, reemerged in 2016. It is likely that the Market Street film survives today because it was sent away before the fire.

Several 35mm prints exist with slight changes in footage. Copies are held at the Library of Congress and the Prelinger Archives. A digital version is viewable online at Internet Archive, YouTube and Wikimedia Commons. In 2010, the film was selected for preservation in the National Film Registry by the Library of Congress.

🔗 Cryptography 🔗 Cryptography/Computer science

In cryptography, power analysis is a form of side channel attack in which the attacker studies the power consumption of a cryptographic hardware device (such as a smart card, tamper-resistant "black box", or integrated circuit). The attack can non-invasively extract cryptographic keys and other secret information from the device.

Simple power analysis (SPA) involves visually interpreting power traces, or graphs of electrical activity over time. Differential power analysis (DPA) is a more advanced form of power analysis, which can allow an attacker to compute the intermediate values within cryptographic computations through statistical analysis of data collected from multiple cryptographic operations. SPA and DPA were introduced to the open cryptology community in 1998 by Paul Kocher, Joshua Jaffe and Benjamin Jun.

🔗 Brands

The AlphaSmart was a brand of portable, battery powered, word-processing keyboards manufactured by NEO Direct, Inc. (formerly Renaissance Learning, Inc, formerly AlphaSmart, Inc., formerly Intelligent Peripheral Devices, Inc.). Originally released in 1993, the first AlphaSmart models were intended for writing on-the-go and could be plugged into a computer to transfer saved written text. The units' portability and long battery life made them valuable to journalists, writers, and students. Later models expanded functionality by spell-checking, running applications, and accessing wireless printers.

The last model, Neo 2, was released in 2007, and production was discontinued by the company in late September 2013, although the company still offers support and software to existing users.

🔗 Animal anatomy 🔗 Neuroscience 🔗 Anatomy 🔗 Anatomy/Neuroanatomy

The enteric nervous system (ENS) or intrinsic nervous system is one of the main divisions of the autonomic nervous system (ANS) and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract. It is capable of acting independently of the sympathetic and parasympathetic nervous systems, although it may be influenced by them. The ENS is also called the second brain.It is derived from neural crest cells.

The enteric nervous system is capable of operating independently of the brain and spinal cord, but does rely on innervation from the autonomic nervous system via the vagus nerve and prevertebral ganglia in healthy subjects. However, studies have shown that the system is operable with a severed vagus nerve. The neurons of the enteric nervous system control the motor functions of the system, in addition to the secretion of gastrointestinal enzymes. These neurons communicate through many neurotransmitters similar to the CNS, including acetylcholine, dopamine, and serotonin. The large presence of serotonin and dopamine in the gut are key areas of research for neurogastroenterologists.

🔗 United States 🔗 Trains 🔗 United States/Texas

Crush, Texas was a temporary "city" established as the site of a one-day publicity stunt in the U.S. state of Texas in 1896. William George Crush, general passenger agent of the Missouri–Kansas–Texas Railroad (popularly known as the "Katy", from its "M-K-T" initials), conceived the idea in order to demonstrate a staged train wreck as a public spectacle. No admission was charged, and train fares to the crash site were offered at the reduced rate of US$2 (equivalent to $61.46 in 2019) from any location in Texas.

As a result, an estimated 40,000 people—more people than lived in the state's second-largest city at the time—attended the exhibition on Tuesday, September 15, 1896. The event planned to showcase the deliberate head-on collision of two unmanned locomotives at high speed; unexpectedly, the impact caused both engine boilers to explode, resulting in a shower of flying debris that killed two people and caused numerous injuries among the spectators.

🔗 Business 🔗 Games

The beer distribution game (also known as the beer game) is a type of gamification that is used to experience typical coordination problems of a supply chain process. It reflects a role-play simulation where several participants play with each other. The game represents a supply chain with a non-coordinated process where problems arise due to lack of information sharing. This game outlines the importance of information sharing, supply chain management and collaboration throughout a supply chain process. Due to lack of information, suppliers, manufacturers, sales people and customers often have an incomplete understanding of what the real demand of an order is. The most interesting part of the game is that each group has no control over another part of the supply chain. Therefore, each group has only significant control over their own part of the supply chain. Each group can highly influence the entire supply chain by ordering too much or too little which can lead to a bullwhip effect. Therefore, the order taking of a group also highly depends on decisions of the other groups.

🔗 Computing 🔗 China 🔗 East Asia 🔗 Writing systems 🔗 Hong Kong

Han unification is an effort by the authors of Unicode and the Universal Character Set to map multiple character sets of the so-called CJK languages into a single set of unified characters. Han characters are a common feature of written Chinese (hanzi), Japanese (kanji), and Korean (hanja).

Modern Chinese, Japanese and Korean typefaces typically use regional or historical variants of a given Han character. In the formulation of Unicode, an attempt was made to unify these variants by considering them different glyphs representing the same "grapheme", or orthographic unit, hence, "Han unification", with the resulting character repertoire sometimes contracted to Unihan.

Unihan can also refer to the Unihan Database maintained by the Unicode Consortium, which provides information about all of the unified Han characters encoded in the Unicode Standard, including mappings to various national and industry standards, indices into standard dictionaries, encoded variants, pronunciations in various languages, and an English definition. The database is available to the public as text files and via an interactive website. The latter also includes representative glyphs and definitions for compound words drawn from the free Japanese EDICT and Chinese CEDICT dictionary projects (which are provided for convenience and are not a formal part of the Unicode Standard).