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🔗 Biography 🔗 Internet 🔗 Computing 🔗 Computer science 🔗 Biography/science and academia 🔗 Computing/Computer science 🔗 Computing/Early computers 🔗 Computing/Networking

Jonathan Bruce Postel (; August 6, 1943 – October 16, 1998) was an American computer scientist who made many significant contributions to the development of the Internet, particularly with respect to standards. He is known principally for being the Editor of the Request for Comment (RFC) document series, for Simple Mail Transfer Protocol (SMTP), and for administering the Internet Assigned Numbers Authority (IANA) until his death. In his lifetime he was known as the "god of the Internet" for his comprehensive influence on the medium.

The Internet Society's Postel Award is named in his honor, as is the Postel Center at Information Sciences Institute, University of Southern California. His obituary was written by Vint Cerf and published as RFC 2468 in remembrance of Postel and his work. In 2012, Postel was inducted into the Internet Hall of Fame by the Internet Society. The Channel Islands' Domain Registry building was named after him in early 2016.

🔗 Cryptography 🔗 Cryptography/Computer science

In cryptography, a random oracle is an oracle (a theoretical black box) that responds to every unique query with a (truly) random response chosen uniformly from its output domain. If a query is repeated, it responds the same way every time that query is submitted.

Stated differently, a random oracle is a mathematical function chosen uniformly at random, that is, a function mapping each possible query to a (fixed) random response from its output domain.

Random oracles as a mathematical abstraction were firstly used in rigorous cryptographic proofs in the 1993 publication by Mihir Bellare and Phillip Rogaway (1993). They are typically used when the proof cannot be carried out using weaker assumptions on the cryptographic hash function. A system that is proven secure when every hash function is replaced by a random oracle is described as being secure in the random oracle model, as opposed to secure in the standard model of cryptography.

🔗 Writing systems

Shorthand is an abbreviated symbolic writing method that increases speed and brevity of writing as compared to longhand, a more common method of writing a language. The process of writing in shorthand is called stenography, from the Greek stenos (narrow) and graphein (to write). It has also been called brachygraphy, from Greek brachys (short), and tachygraphy, from Greek tachys (swift, speedy), depending on whether compression or speed of writing is the goal.

Many forms of shorthand exist. A typical shorthand system provides symbols or abbreviations for words and common phrases, which can allow someone well-trained in the system to write as quickly as people speak. Abbreviation methods are alphabet-based and use different abbreviating approaches. Many journalists use shorthand writing to quickly take notes at press conferences or other similar scenarios. In the computerized world, several autocomplete programs, standalone or integrated in text editors, based on word lists, also include a shorthand function for frequently used phrases.

Shorthand was used more widely in the past, before the invention of recording and dictation machines. Shorthand was considered an essential part of secretarial training and police work and was useful for journalists. Although the primary use of shorthand has been to record oral dictation or discourse, some systems are used for compact expression. For example, healthcare professionals may use shorthand notes in medical charts and correspondence. Shorthand notes are typically temporary, intended either for immediate use or for later typing, data entry, or (mainly historically) transcription to longhand. Longer term uses do exist, such as encipherment: diaries (like that of Samuel Pepys) are a common example.

🔗 Computing

DjVu ( DAY-zhah-VOO, like French "déjà vu") is a computer file format designed primarily to store scanned documents, especially those containing a combination of text, line drawings, indexed color images, and photographs. It uses technologies such as image layer separation of text and background/images, progressive loading, arithmetic coding, and lossy compression for bitonal (monochrome) images. This allows high-quality, readable images to be stored in a minimum of space, so that they can be made available on the web.

DjVu has been promoted as providing smaller files than PDF for most scanned documents. The DjVu developers report that color magazine pages compress to 40–70 kB, black-and-white technical papers compress to 15–40 kB, and ancient manuscripts compress to around 100 kB; a satisfactory JPEG image typically requires 500 kB. Like PDF, DjVu can contain an OCR text layer, making it easy to perform copy and paste and text search operations.

Free creators, manipulators, converters, browser plug-ins, and desktop viewers are available. DjVu is supported by a number of multi-format document viewers and e-book reader software on Linux (Okular, Evince), Windows (SumatraPDF), Android (EBookDroid, PocketBook).

🔗 Philosophy 🔗 Philosophy/Logic 🔗 Philosophy/Epistemology

The unexpected hanging paradox or hangman paradox is a paradox about a person's expectations about the timing of a future event which they are told will occur at an unexpected time. The paradox is variously applied to a prisoner's hanging, or a surprise school test. It could be reduced to be Moore's paradox.

Despite significant academic interest, there is no consensus on its precise nature and consequently a final correct resolution has not yet been established. Logical analysis suggests that the problem arises in a self-contradictory self-referencing statement at the heart of the judge's sentence. Epistemological studies of the paradox have suggested that it turns on our concept of knowledge. Even though it is apparently simple, the paradox's underlying complexities have even led to its being called a "significant problem" for philosophy.

🔗 Computer science 🔗 Mathematics

A negative base (or negative radix) may be used to construct a non-standard positional numeral system. Like other place-value systems, each position holds multiples of the appropriate power of the system's base; but that base is negative—that is to say, the base b is equal to −r for some natural number r (r ≥ 2).

Negative-base systems can accommodate all the same numbers as standard place-value systems, but both positive and negative numbers are represented without the use of a minus sign (or, in computer representation, a sign bit); this advantage is countered by an increased complexity of arithmetic operations. The need to store the information normally contained by a negative sign often results in a negative-base number being one digit longer than its positive-base equivalent.

The common names for negative-base positional numeral systems are formed by prefixing nega- to the name of the corresponding positive-base system; for example, negadecimal (base −10) corresponds to decimal (base 10), negabinary (base −2) to binary (base 2), negaternary (base −3) to ternary (base 3), and negaquaternary (base −4) to quaternary (base 4).

🔗 Mathematics

The Trachtenberg system is a system of rapid mental calculation. The system consists of a number of readily memorized operations that allow one to perform arithmetic computations very quickly. It was developed by the Russian Jewish engineer Jakow Trachtenberg in order to keep his mind occupied while being in a Nazi concentration camp.

The rest of this article presents some methods devised by Trachtenberg. Some of the algorithms Trachtenberg developed are ones for general multiplication, division and addition. Also, the Trachtenberg system includes some specialised methods for multiplying small numbers between 5 and 13.

The section on addition demonstrates an effective method of checking calculations that can also be applied to multiplication.

🔗 Books 🔗 Business 🔗 Comics 🔗 Comics/Comic strips

The Dilbert principle is a concept in management developed by Scott Adams, creator of the comic strip Dilbert, which states that companies tend to systematically promote incompetent employees to management to get them out of the workflow. The Dilbert principle is inspired by the Peter principle, which holds that employees are promoted based on success in their current position until they reach their "level of incompetence" and are no longer promoted. Under the Dilbert principle, employees who were never competent are promoted to management to limit the damage they can do. Adams first explained the principle in a 1995 Wall Street Journal article, and expanded upon it in his 1996 business book The Dilbert Principle.

🔗 Russia 🔗 Russia/technology and engineering in Russia 🔗 Russia/science and education in Russia 🔗 Geology

The Kola Superdeep Borehole (Russian: Кольская сверхглубокая скважина) is the result of a scientific drilling project of the Soviet Union in the Pechengsky District, on the Kola Peninsula. The project attempted to drill as deep as possible into the Earth's crust. Drilling began on 24 May 1970 using the Uralmash-4E, and later the Uralmash-15000 series drilling rig. Boreholes were drilled by branching from a central hole. The deepest, SG-3, reached 12,262 metres (40,230 ft; 7.619 mi) in 1989 and is the deepest artificial point on Earth. The borehole is 23 centimetres (9 in) in diameter.

In terms of true vertical depth, it is the deepest borehole in the world. For two decades it was also the world's longest borehole in terms of measured depth along the well bore, until it was surpassed in 2008 by the 12,289-metre-long (40,318 ft) Al Shaheen oil well in Qatar, and in 2011 by the 12,345-metre-long (40,502 ft) Sakhalin-I Odoptu OP-11 Well (offshore from the Russian island of Sakhalin).

🔗 Mathematics

Wikipedia provides one of the more prominent resources on the Web for factual information about contemporary mathematics, with over 20,000 articles on mathematical topics. It is natural that many readers use Wikipedia for the purpose of self-study in mathematics and its applications. Some readers will be simultaneously studying mathematics in a more formal way, while others will rely on Wikipedia alone. There are certain points that need to be kept in mind by anyone using Wikipedia for mathematical self-study, in order to make the best use of what is here, perhaps in conjunction with other resources.