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🔗 Biography 🔗 Mathematics 🔗 Military history 🔗 Military history/Military biography 🔗 Cryptography 🔗 Cryptography/Computer science 🔗 Military history/European military history 🔗 Military history/British military history

William Thomas "Bill" Tutte OC FRS FRSC (; 14 May 1917 – 2 May 2002) was a British codebreaker and mathematician. During the Second World War, he made a brilliant and fundamental advance in cryptanalysis of the Lorenz cipher, a major Nazi German cipher system which was used for top-secret communications within the Wehrmacht High Command. The high-level, strategic nature of the intelligence obtained from Tutte's crucial breakthrough, in the bulk decrypting of Lorenz-enciphered messages specifically, contributed greatly, and perhaps even decisively, to the defeat of Nazi Germany. He also had a number of significant mathematical accomplishments, including foundation work in the fields of graph theory and matroid theory.

Tutte's research in the field of graph theory proved to be of remarkable importance. At a time when graph theory was still a primitive subject, Tutte commenced the study of matroids and developed them into a theory by expanding from the work that Hassler Whitney had first developed around the mid 1930s. Even though Tutte's contributions to graph theory have been influential to modern graph theory and many of his theorems have been used to keep making advances in the field, most of his terminology was not in agreement with their conventional usage and thus his terminology is not used by graph theorists today. "Tutte advanced graph theory from a subject with one text (D. Kőnig's) toward its present extremely active state."

🔗 Aviation 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Aviation/aircraft 🔗 Aviation/aircraft engine

The Aircraft Nuclear Propulsion (ANP) program and the preceding Nuclear Energy for the Propulsion of Aircraft (NEPA) project worked to develop a nuclear propulsion system for aircraft. The United States Army Air Forces initiated Project NEPA on May 28, 1946. NEPA operated until May 1951, when the project was transferred to the joint Atomic Energy Commission (AEC)/USAF ANP. The USAF pursued two different systems for nuclear-powered jet engines, the Direct Air Cycle concept, which was developed by General Electric, and Indirect Air Cycle, which was assigned to Pratt & Whitney. The program was intended to develop and test the Convair X-6, but was cancelled in 1961 before that aircraft was built. The total cost of the program from 1946 to 1961 was about $1 billion.

🔗 Energy

A black start is the process of restoring an electric power station or a part of an electric grid to operation without relying on the external electric power transmission network to recover from a total or partial shutdown.

Normally, the electric power used within the plant is provided from the station's own generators. If all of the plant's main generators are shut down, station service power is provided by drawing power from the grid through the plant's transmission line. However, during a wide-area outage, off-site power from the grid is not available. In the absence of grid power, a so-called black start needs to be performed to bootstrap the power grid into operation.

To provide a black start, some power stations have small diesel generators, normally called the black start diesel generator (BSDG), which can be used to start larger generators (of several megawatts capacity), which in turn can be used to start the main power station generators. Generating plants using steam turbines require station service power of up to 10% of their capacity for boiler feedwater pumps, boiler forced-draft combustion air blowers, and for fuel preparation. It is uneconomical to provide such a large standby capacity at each station, so black-start power must be provided over designated tie lines from another station. Often hydroelectric power plants are designated as the black-start sources to restore network interconnections. A hydroelectric station needs very little initial power for starting purposes (just enough to open the intake gates and provide excitation current to the generator field coils), and can put a large block of power on line very quickly to allow start-up of fossil-fuel or nuclear stations. Certain types of combustion turbine can be configured for black start, providing another option in places without suitable hydroelectric plants. In 2017, a utility in Southern California successfully demonstrated the use of a battery-based energy-storage system to provide a black start, firing up a combined-cycle gas turbine from an idle state.

🔗 Computer science 🔗 Mathematics 🔗 Systems 🔗 Cryptography 🔗 Cryptography/Computer science 🔗 Systems/Operations research

The knapsack problem is a problem in combinatorial optimization: Given a set of items, each with a weight and a value, determine the number of each item to include in a collection so that the total weight is less than or equal to a given limit and the total value is as large as possible. It derives its name from the problem faced by someone who is constrained by a fixed-size knapsack and must fill it with the most valuable items. The problem often arises in resource allocation where the decision makers have to choose from a set of non-divisible projects or tasks under a fixed budget or time constraint, respectively.

The knapsack problem has been studied for more than a century, with early works dating as far back as 1897. The name "knapsack problem" dates back to the early works of mathematician Tobias Dantzig (1884–1956), and refers to the commonplace problem of packing the most valuable or useful items without overloading the luggage.

🔗 United States 🔗 Books 🔗 Reference works 🔗 English Language

The New Oxford American Dictionary (NOAD) is a single-volume dictionary of American English compiled by American editors at the Oxford University Press.

NOAD is based upon the New Oxford Dictionary of English (NODE), published in the United Kingdom in 1998, although with substantial editing, additional entries, and the inclusion of illustrations. It is based on a corpus linguistics analysis of Oxford's 200 million word database of contemporary American English.

NOAD includes a diacritical respelling scheme to convey pronunciations, as opposed to the Gimson phonemic IPA system that is used in NODE.

🔗 Cryptography 🔗 Cryptography/Computer science

In cryptography, a zero-knowledge proof or zero-knowledge protocol is a method by which one party (the prover) can prove to another party (the verifier) that they know a value x, without conveying any information apart from the fact that they know the value x. The essence of zero-knowledge proofs is that it is trivial to prove that one possesses knowledge of certain information by simply revealing it; the challenge is to prove such possession without revealing the information itself or any additional information.

If proving a statement requires that the prover possesses some secret information, then the verifier will not be able to prove the statement to anyone else without possessing the secret information. The statement being proved must include the assertion that the prover has such knowledge, but not the knowledge itself. Otherwise, the statement would not be proved in zero-knowledge because it provides the verifier with additional information about the statement by the end of the protocol. A zero-knowledge proof of knowledge is a special case when the statement consists only of the fact that the prover possesses the secret information.

Interactive zero-knowledge proofs require interaction between the individual (or computer system) proving their knowledge and the individual validating the proof.

A protocol implementing zero-knowledge proofs of knowledge must necessarily require interactive input from the verifier. This interactive input is usually in the form of one or more challenges such that the responses from the prover will convince the verifier if and only if the statement is true, i.e., if the prover does possess the claimed knowledge. If this were not the case, the verifier could record the execution of the protocol and replay it to convince someone else that they possess the secret information. The new party's acceptance is either justified since the replayer does possess the information (which implies that the protocol leaked information, and thus, is not proved in zero-knowledge), or the acceptance is spurious, i.e., was accepted from someone who does not actually possess the information.

Some forms of non-interactive zero-knowledge proofs exist, but the validity of the proof relies on computational assumptions (typically the assumptions of an ideal cryptographic hash function).

🔗 Linguistics 🔗 Linguistics/Applied Linguistics 🔗 Judaism 🔗 Israel

The revival of the Hebrew language took place in Europe and Palestine toward the end of the 19th century and into the 20th century, through which the language's usage changed from the sacred language of Judaism to a spoken and written language used for daily life in Israel. The process began as a diversity of Jews started arriving and establishing themselves alongside the pre-existing Jewish community in the region of Palestine in the first half of the nineteenth century, when veteran Jews in Palestine (largely Arabic-speaking by that time) and the linguistically diverse newly arrived Jews all switched to use Hebrew as a lingua franca, the historical linguistic common denominator of all the Jewish groups. At the same time, a parallel development in Europe changed Hebrew from primarily a sacred liturgical language into a literary language which played a key role in the development of nationalist educational programs. Modern Hebrew was one of three official languages of Mandatory Palestine, and after the Israeli Declaration of Independence in 1948, one of two official languages of Israel, along with Modern Arabic. In July 2018, a new law made Hebrew the sole official language of the state of Israel, with Arabic having "special status". More than purely a linguistic process, the revival of Hebrew was utilized by Jewish modernization and political movements, and became a tenet of the ideology associated with settlement of the land, Zionism and Israeli policy.

The process of Hebrew's return to regular usage is unique; there are no other examples of a natural language without any native speakers subsequently acquiring several million native speakers, and no other examples of a sacred language becoming a national language with millions of "first language" speakers.

The language's revival eventually brought linguistic additions with it. While the initial leaders of the process insisted they were only continuing "from the place where Hebrew's vitality was ended", what was created represented a broader basis of language acceptance; it includes characteristics derived from all periods of Hebrew language, as well as from the non-Hebrew languages used by the long-established European, North African, and Middle Eastern Jewish communities, with Yiddish (the European variant) being predominant.

🔗 Companies 🔗 Internet 🔗 Crime 🔗 Finance & Investment 🔗 Numismatics 🔗 Websites 🔗 Websites/Computing 🔗 Numismatics/Cryptocurrency 🔗 Cryptocurrency

Mt. Gox was a bitcoin exchange based in Shibuya, Tokyo, Japan. Launched in July 2010, by 2013 and into 2014 it was handling over 70% of all bitcoin (BTC) transactions worldwide, as the largest bitcoin intermediary and the world's leading bitcoin exchange.

In February 2014, Mt. Gox suspended trading, closed its website and exchange service, and filed for bankruptcy protection from creditors. In April 2014, the company began liquidation proceedings.

Mt. Gox announced that approximately 850,000 bitcoins belonging to customers and the company were missing and likely stolen, an amount valued at more than $450 million at the time. Although 200,000 bitcoins have since been "found", the reasons for the disappearance—theft, fraud, mismanagement, or a combination of these—were initially unclear. New evidence presented in April 2015 by Tokyo security company WizSec led them to conclude that "most or all of the missing bitcoins were stolen straight out of the Mt. Gox hot wallet over time, beginning in late 2011."

🔗 Computing 🔗 Computing/Software 🔗 Computing/Free and open-source software 🔗 Plan 9

Plan 9 from Bell Labs is a distributed operating system, originating in the Computing Science Research Center (CSRC) at Bell Labs in the mid-1980s, and building on UNIX concepts first developed there in the late 1960s. The final official release was in early 2015.

Under Plan 9, UNIX's everything is a file metaphor is extended via a pervasive network-centric filesystem, and graphical user interface is assumed as a basis for almost all functionality, though it retains a heavily text-centric ideology.

The name Plan 9 from Bell Labs is a reference to the Ed Wood 1959 cult science fiction Z-movie Plan 9 from Outer Space. The name of the project's mascot is "Glenda, the Plan 9 Bunny". The system continues to be used and developed by operating system researchers and hobbyists.

🔗 Typography 🔗 Industrial design

The IBM Selectric typewriter was a highly successful line of electric typewriters introduced by IBM on 31 July 1961.

Instead of the "basket" of individual typebars that swung up to strike the ribbon and page in a typical typewriter of the period, the Selectric had an "element" (frequently called a "typeball", or less formally, a "golf ball") that rotated and pivoted to the correct position before striking. The element could be easily changed so as to use different fonts in the same document typed on the same typewriter, resurrecting a capability that had been pioneered by typewriters such as the Hammond and Blickensderfer in the late 19th century. The Selectric also replaced the traditional typewriter's horizontally moving carriage with a roller (platen) that turned to advance the paper but did not move horizontally, while the typeball and ribbon mechanism did.

The Selectric mechanism was notable for using internal mechanical binary coding and two mechanical digital-to-analog converters, called whiffletree linkages, to select the character to be typed.

Selectrics and their descendants eventually captured 75 percent of the United States market for electric typewriters used in business. IBM replaced the Selectric line with the IBM Wheelwriter in 1984 and transferred its typewriter business to the newly formed Lexmark in 1991. By its 25th anniversary, in 1986, a total of more than 13 million machines were made and sold.