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🔗 Statistics

Extreme learning machines are feedforward neural networks for classification, regression, clustering, sparse approximation, compression and feature learning with a single layer or multiple layers of hidden nodes, where the parameters of hidden nodes (not just the weights connecting inputs to hidden nodes) need not be tuned. These hidden nodes can be randomly assigned and never updated (i.e. they are random projection but with nonlinear transforms), or can be inherited from their ancestors without being changed. In most cases, the output weights of hidden nodes are usually learned in a single step, which essentially amounts to learning a linear model. The name "extreme learning machine" (ELM) was given to such models by its main inventor Guang-Bin Huang.

According to their creators, these models are able to produce good generalization performance and learn thousands of times faster than networks trained using backpropagation. In literature, it also shows that these models can outperform support vector machines (SVM) and SVM provides suboptimal solutions in both classification and regression applications.

🔗 Companies 🔗 Germany 🔗 Transport 🔗 Energy 🔗 Transport/Maritime 🔗 Ships

SkySails GmbH & Co. KG is a Hamburg-based company that sells kite rigs to propel cargo ships, large yachts and fishing vessels by wind energy. Ships are pulled by an automatically-controlled foil kite of some hundreds of square meters. For multiple reasons, they give many times the thrust per unit area of conventional mast-mounted sails.

The systems save fuel, and reduce carbon emissions and shipping costs, but have not been widely adopted.

🔗 History 🔗 Lists 🔗 Business

This is a list of obsolete occupations. To be included in this list an occupation must be completely, or to a great extent, obsolete. For example, there are still a few lamplighters retained for ceremonial or tourist purposes, but in the main the occupation is now obsolete. Similarly, there are still some manual switchboard operators and elevator operators which are required for historic equipment or security reasons, but these are now considered to be obsolete occupations. Occupations which appear to be obsolete in industrialized countries may still be carried out commercially in other parts of the world, for example charcoal burner.

To be included in this list an obsolete occupation should in the past have employed significant numbers of workers (hundreds or thousands as evidenced by, for example, census data). Some rare occupations are included in this list, but only if they have notable practitioners, for example alchemist or phrenologist.

Terms which describe groups of people carrying out a variety of roles, but which are not specific occupations, are excluded from this list even if they are obsolete, for example conquistador or retinue. Terms describing positions which have a modern equivalent, and are thus not obsolete occupations, are excluded from this list, for example a dragoman would now be termed a diplomat; similarly a cunning woman would now be termed a practitioner of folk medicine. Terms describing a state of being rather than an occupation are excluded, for example castrato. Specialist terms for an occupation, even if they are obsolete, are excluded, for example the numerous historic terms for cavalry and courtesan. Foreign language terms for existing occupations are excluded, for example korobeinik or Laukkuryssä which are types of peddler. All types of forced labour, such as slavery and penal labour are excluded from this list as they are not paid occupations.

Only occupations which are notable, well-defined, and adequately documented in secondary sources are included in this list.

🔗 Computing

FRACTRAN is a Turing-complete esoteric programming language invented by the mathematician John Conway. A FRACTRAN program is an ordered list of positive fractions together with an initial positive integer input n. The program is run by updating the integer n as follows:

1. for the first fraction f in the list for which nf is an integer, replace n by nf
2. repeat this rule until no fraction in the list produces an integer when multiplied by n, then halt.

Conway 1987 gives the following formula for primes in FRACTRAN:

${\displaystyle \left({\frac {17}{91}},{\frac {78}{85}},{\frac {19}{51}},{\frac {23}{38}},{\frac {29}{33}},{\frac {77}{29}},{\frac {95}{23}},{\frac {77}{19}},{\frac {1}{17}},{\frac {11}{13}},{\frac {13}{11}},{\frac {15}{2}},{\frac {1}{7}},{\frac {55}{1}}\right)}$

Starting with n=2, this FRACTRAN program generates the following sequence of integers:

2, 15, 825, 725, 1925, 2275, 425, 390, 330, 290, 770, ... (sequence A007542 in the OEIS)

After 2, this sequence contains the following powers of 2:

${\displaystyle 2^{2}=4,\,2^{3}=8,\,2^{5}=32,\,2^{7}=128,\,2^{11}=2048,\,2^{13}=8192,\,2^{17}=131072,\,2^{19}=524288,\,\dots }$ (sequence A034785 in the OEIS)

which are the prime powers of 2.

🔗 Astronomy 🔗 Astronomy/Astronomical objects

TON 618 (short for Tonantzintla 618) is a hyperluminous, broad-absorption-line, radio-loud quasar and Lyman-alpha blob located near the border of the constellations Canes Venatici and Coma Berenices, with the projected comoving distance of approximately 18.2 billion light-years from Earth. It possesses one of the most massive black holes ever found, at 40 billion M_☉.

🔗 Computing 🔗 Computing/Software 🔗 Linguistics 🔗 Computing/Computer science 🔗 Linguistics/Applied Linguistics

Mark V. Shaney is a synthetic Usenet user whose postings in the net.singles newsgroups were generated by Markov chain techniques, based on text from other postings. The username is a play on the words "Markov chain". Many readers were fooled into thinking that the quirky, sometimes uncannily topical posts were written by a real person.

The system was designed by Rob Pike with coding by Bruce Ellis. Don P. Mitchell wrote the Markov chain code, initially demonstrating it to Pike and Ellis using the Tao Te Ching as a basis. They chose to apply it to the net.singles netnews group.

🔗 Mathematics

Toom–Cook, sometimes known as Toom-3, named after Andrei Toom, who introduced the new algorithm with its low complexity, and Stephen Cook, who cleaned the description of it, is a multiplication algorithm for large integers.

Given two large integers, a and b, Toom–Cook splits up a and b into k smaller parts each of length l, and performs operations on the parts. As k grows, one may combine many of the multiplication sub-operations, thus reducing the overall complexity of the algorithm. The multiplication sub-operations can then be computed recursively using Toom–Cook multiplication again, and so on. Although the terms "Toom-3" and "Toom–Cook" are sometimes incorrectly used interchangeably, Toom-3 is only a single instance of the Toom–Cook algorithm, where k = 3.

Toom-3 reduces 9 multiplications to 5, and runs in Θ(n^{log(5)/log(3)}) ≈ Θ(n^1.46). In general, Toom-k runs in Θ(c(k) n^e), where e = log(2k − 1) / log(k), n^e is the time spent on sub-multiplications, and c is the time spent on additions and multiplication by small constants. The Karatsuba algorithm is a special case of Toom–Cook, where the number is split into two smaller ones. It reduces 4 multiplications to 3 and so operates at Θ(n^{log(3)/log(2)}) ≈ Θ(n^1.58). Ordinary long multiplication is equivalent to Toom-1, with complexity Θ(n²).

Although the exponent e can be set arbitrarily close to 1 by increasing k, the function c unfortunately grows very rapidly. The growth rate for mixed-level Toom–Cook schemes was still an open research problem in 2005. An implementation described by Donald Knuth achieves the time complexity Θ(n 2^{√2 log n} log n).

Due to its overhead, Toom–Cook is slower than long multiplication with small numbers, and it is therefore typically used for intermediate-size multiplications, before the asymptotically faster Schönhage–Strassen algorithm (with complexity Θ(n log n log log n)) becomes practical.

Toom first described this algorithm in 1963, and Cook published an improved (asymptotically equivalent) algorithm in his PhD thesis in 1966.

🔗 United States 🔗 Companies 🔗 United States/Washington - Seattle 🔗 United States/Washington 🔗 Fashion

Nordstrom, Inc. () is an American luxury department store chain founded in 1901 by John W. Nordstrom and Carl F. Wallin. It originated as a shoe store, and evolved into a full-line retailer with departments for clothing, footwear, handbags, jewelry, accessories, cosmetics, and fragrances. Some stores feature home furnishings and wedding departments, and several have in-house cafes, restaurants, and espresso bars.

As of 2020, Nordstrom operates 117 stores in 40 U.S. states, three Canadian provinces, and Puerto Rico. The corporate headquarters and flagship store are located in the former Frederick & Nelson building in Seattle, Washington; a second flagship store is located near Columbus Circle in New York City. Its subsidiaries include the off-price department store chain Nordstrom Rack and the members-only online store HauteLook.

🔗 Archaeology 🔗 Museums 🔗 Merseyside

The Williamson Tunnels are a series of extensive subterranean excavations, of unknown purpose, in the Edge Hill area of Liverpool, England. They are thought to have been created under the direction of tobacco merchant, landowner and philanthropist Joseph Williamson between 1810 and 1840. Although popularly described as "tunnels", the majority comprise brick or stone vaulting over excavations in the underlying sandstone. The purpose of the works remains unclear and remains a subject of heavy speculation; suggestions include commercial quarrying, a philanthropic desire to provide employment, and Williamson's own eccentric interests.

After being gradually infilled with rubble and spoil during the late 19th and early 20th centuries, they remained largely inaccessible until archaeological investigations were carried out in 1995. Since then volunteers have rediscovered and excavated an extensive network of tunnels, chambers and voids across several sites, with sections open to the public. Guided tours are available at the Williamson Tunnels Heritage Centre and the Friends Of Williamson's Tunnels, and excavation continues as volunteers continue to uncover new sections.

🔗 Time 🔗 Solar System/Mars 🔗 Solar System

Various schemes have been used or proposed for timekeeping on the planet Mars independently of Earth time and calendars.

Mars has an axial tilt and a rotation period similar to those of Earth. Thus, it experiences seasons of spring, summer, autumn and winter much like Earth. Coincidentally, the duration of a Martian day is within a few percent of that of an Earth day, which has led to the use of analogous time units. A Mars year is almost twice as long as Earth's, and its orbital eccentricity is considerably larger, which means that the lengths of various Martian seasons differ considerably, and sundial time can diverge from clock time more than on Earth.