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A rotary woofer is a subwoofer-style loudspeaker which reproduces very low frequency content by using a conventional speaker voice coil's motion to change the pitch (angle) of the blades of an impeller rotating at a constant speed. The pitch of the fan blades is controlled by the audio signal presented to the voice coil, and is able to swing both positive and negative, with respect to a zero pitch spinning blade position. Since the audio amplifier only changes the pitch of the blades, it takes much less power, per dB of generated acoustic sound level, to drive a rotary woofer than to power a conventional subwoofer, which uses a moving electromagnet (voice coil) placed within the field of a stationary permanent magnet to drive a cone which then displaces air. Rotary woofers excel at producing sounds below 20 Hz, below the normal hearing range; when installed in the wall of a sealed room, they can produce audio frequencies down to 0 Hz, a static pressure differential, by simply compressing the air in the sealed room.

🔗 Poetry

"The Gods of the Copybook Headings" is a poem by Rudyard Kipling, characterized by biographer Sir David Gilmour as one of several "ferocious post-war eruptions" of Kipling's souring sentiment concerning the state of Anglo-European society. It was first published in the Sunday Pictorial of London on 26 October 1919; in America, it was published as "The Gods of the Copybook Maxims" in Harper's Magazine in January 1920.

In the poem, Kipling's narrator counterposes the "Gods" of the title, who embody eternal truths, against "the Gods of the Market-Place", who represent an optimistic self-deception into which it supposes society has fallen in the early 20th century.

The "copybook headings" to which the title refers were proverbs or maxims, often drawn from sermons and scripture extolling virtue and wisdom, that were printed at the top of the pages of copybooks, special notebooks used by 19th-century British schoolchildren. The students had to copy the maxims repeatedly, by hand, down the page. The exercise was thought to serve simultaneously as a form of moral education and penmanship practice.

🔗 Aviation 🔗 Military history 🔗 Military history/Military aviation 🔗 Engineering 🔗 Industrial design

Speed tape is an aluminium pressure-sensitive tape used to perform minor repairs on aircraft and racing cars. It is used as a temporary repair material until a more permanent repair can be carried out. It has an appearance similar to duct tape, for which it is sometimes mistaken, but its adhesive is capable of sticking on an airplane fuselage or wing at high speeds, hence the name.

🔗 Disaster management 🔗 Africa 🔗 Greece 🔗 Turkey 🔗 Bulgaria 🔗 Africa/Libya 🔗 Weather 🔗 Weather/Non-tropical storms 🔗 Weather/Floods 🔗 Weather/Weather 🔗 Africa/Egypt 🔗 Weather/Tropical cyclones

Storm Daniel, also known as Cyclone Daniel, was the deadliest Mediterranean tropical-like cyclone ever recorded as well as the deadliest weather event during 2023. It caused catastrophic damage in Libya and also affected parts of southeastern Europe. Forming as a low-pressure system around 4 September 2023, the storm affected Greece, Bulgaria and also Turkey with extensive flooding. The storm then organized as a Mediterranean Low and was designated as Storm Daniel, in which it soon acquired quasi-tropical characteristics (TLC) and moved toward the coast of Libya, where it caused catastrophic flooding before degenerating into a remnant low. The storm was the result of an Omega block, as a high-pressure zone became sandwiched between two zones of low pressure, the isobars shaping a Greek letter Ω.

🔗 Medicine

The Therac-25 was a computer-controlled radiation therapy machine produced by Atomic Energy of Canada Limited (AECL) in 1982 after the Therac-6 and Therac-20 units (the earlier units had been produced in partnership with CGR of France).

It was involved in at least six accidents between 1985 and 1987, in which patients were given massive overdoses of radiation. Because of concurrent programming errors, it sometimes gave its patients radiation doses that were hundreds of times greater than normal, resulting in death or serious injury. These accidents highlighted the dangers of software control of safety-critical systems, and they have become a standard case study in health informatics and software engineering. Additionally the overconfidence of the engineers and lack of proper due diligence to resolve reported software bugs are highlighted as an extreme case where the engineers' overconfidence in their initial work and failure to believe the end users' claims caused drastic repercussions.

🔗 Lists 🔗 Photography 🔗 Photography/History of photography

This is a list of photographs considered the most important in surveys where authoritative sources review the history of the medium not limited by time period, region, genre, topic, or other specific criteria. These images may be referred to as the most important, most iconic, or most influential—but they are all considered key images in the history of photography.

🔗 Animation

Rubber hose animation was the first animation style that became standardized in the American animation field. The defining feature is the curving motion most things possess, resembling that of a rubber hose. While the style fell out of fashion during the 1930s, there has been a minor revitalization of it in recent years with works such as the video games Cuphead and Bendy and the Ink Machine, and the film Steven Universe: The Movie.

🔗 Technology

KarTrak, sometimes KarTrak ACI (for Automatic Car Identification) is a colored bar code system designed to automatically identify rail cars and other rolling stock. KarTrak was made a requirement in North America, but technical problems led to abandonment of the system in the late 1970s.

🔗 United States 🔗 Comedy 🔗 Journalism

The Order of the Occult Hand is a secret society of American journalists who slip the meaningless and telltale phrase "It was as if an occult hand had…" in print as an inside joke.

🔗 Africa 🔗 Highways 🔗 Highways/Road transport 🔗 Highways/African Highways

The Trans-African Highway network comprises transcontinental road projects in Africa being developed by the United Nations Economic Commission for Africa (UNECA), the African Development Bank (ADB), and the African Union in conjunction with regional international communities. They aim to promote trade and alleviate poverty in Africa through highway infrastructure development and the management of road-based trade corridors. The total length of the nine highways in the network is 56,683 km (35,221 mi).

In some documents the highways are referred to as "Trans-African Corridors" or "Road Corridors" rather than highways. The name Trans-African Highway and its variants are not in wide common usage outside of planning and development circles, and as of 2014 one does not see them signposted as such or labelled on maps, except in Kenya and Uganda where the Mombasa–Nairobi–Kampala–Fort Portal section (or the Kampala–Kigali feeder road) of Trans-African Highway 8 is sometimes referred to as the "Trans-Africa Highway".