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🔗 Cycling 🔗 Motorcycling

Countersteering is used by single-track vehicle operators, such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering counter to the desired direction ("steer left to turn right"). To negotiate a turn successfully, the combined center of mass of the rider and the single-track vehicle must first be leaned in the direction of the turn, and steering briefly in the opposite direction causes that lean. The rider's action of countersteering is sometimes referred to as "giving a steering command".^: 15

The scientific literature does not provide a clear and comprehensive definition of countersteering. In fact, "a proper distinction between steer torque and steer angle ... is not always made."

🔗 Mathematics 🔗 Statistics

The secretary problem is a problem that demonstrates a scenario involving optimal stopping theory. The problem has been studied extensively in the fields of applied probability, statistics, and decision theory. It is also known as the marriage problem, the sultan's dowry problem, the fussy suitor problem, the googol game, and the best choice problem.

The basic form of the problem is the following: imagine an administrator who wants to hire the best secretary out of ${\displaystyle n}$ rankable applicants for a position. The applicants are interviewed one by one in random order. A decision about each particular applicant is to be made immediately after the interview. Once rejected, an applicant cannot be recalled. During the interview, the administrator gains information sufficient to rank the applicant among all applicants interviewed so far, but is unaware of the quality of yet unseen applicants. The question is about the optimal strategy (stopping rule) to maximize the probability of selecting the best applicant. If the decision can be deferred to the end, this can be solved by the simple maximum selection algorithm of tracking the running maximum (and who achieved it), and selecting the overall maximum at the end. The difficulty is that the decision must be made immediately.

The shortest rigorous proof known so far is provided by the odds algorithm (Bruss 2000). It implies that the optimal win probability is always at least ${\displaystyle 1/e}$ (where e is the base of the natural logarithm), and that the latter holds even in a much greater generality (2003). The optimal stopping rule prescribes always rejecting the first ${\displaystyle \sim n/e}$ applicants that are interviewed and then stopping at the first applicant who is better than every applicant interviewed so far (or continuing to the last applicant if this never occurs). Sometimes this strategy is called the ${\displaystyle 1/e}$ stopping rule, because the probability of stopping at the best applicant with this strategy is about ${\displaystyle 1/e}$ already for moderate values of ${\displaystyle n}$. One reason why the secretary problem has received so much attention is that the optimal policy for the problem (the stopping rule) is simple and selects the single best candidate about 37% of the time, irrespective of whether there are 100 or 100 million applicants.

🔗 Spaceflight 🔗 Rocketry 🔗 Science 🔗 Photography

The V-2 No. 13 was a modified V-2 rocket that became the first object to take a photograph of the Earth from outer space. Launched on 24 October 1946, at the White Sands Missile Range in White Sands, New Mexico, the rocket reached a maximum altitude of 65 mi (105 km).

🔗 Internet culture 🔗 Climate change 🔗 Environment 🔗 United Kingdom 🔗 Antarctica 🔗 Arctic 🔗 Oceans 🔗 Antarctica/British Antarctic Territory

Boaty McBoatface (also known as Boaty) is the British lead boat in a fleet of three robotic lithium battery–powered autonomous underwater vehicles (AUVs) of the Autosub Long Range (ALR) class. Launched in 2017 and carried on board the polar scientific research vessel RRS Sir David Attenborough, she is a focal point of the Polar Explorer Programme of the UK Government.

Boaty and her two fleet-mates are part of the UK National Marine Equipment Pool and owned by the National Oceanography Centre in Southampton. She is classified as an "autosub long range (ALR) autonomous underwater vehicle", and will use her onboard sensors to map the movement of deep waters that play a vital role in regulating the Earth's climate.

🔗 Sports

Naismith's rule helps with the planning of a walking or hiking expedition by calculating how long it will take to travel the intended route, including any extra time taken when walking uphill. This rule of thumb was devised by William W. Naismith, a Scottish mountaineer, in 1892. A modern version can be formulated as follows:

Allow one hour for every 3 miles (5 km) forward, plus an additional hour for every 2,000 feet (600 m) of ascent.

🔗 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).

🔗 France 🔗 Cycling

The Passage du Gois (French pronunciation: [pasaʒ dy ɡwa]) or Gôa is a causeway between Beauvoir-sur-Mer and the island of Noirmoutier, in Vendée on the Atlantic coast of France. The causeway is 4.125 kilometres (2.6 mi) long and is flooded twice a day by the high tide. A road runs along the causeway.

Every year, a foot race – the Foulées du Gois – is held across it, starting at the onset of high tide.

🔗 California 🔗 Energy 🔗 California/Southern California

The Santa Susana Field Laboratory is a complex of industrial research and development facilities located on a 2,668-acre (1,080 ha) portion of the Southern California Simi Hills in Simi Valley, California. It was used mainly for the development and testing of liquid-propellant rocket engines for the United States space program from 1949 to 2006, nuclear reactors from 1953 to 1980 and the operation of a U.S. government-sponsored liquid metals research center from 1966 to 1998. The site is located approximately 7 miles (11 km) northwest from the community of Canoga Park and approximately 30 miles (48 km) northwest of Downtown Los Angeles. Sage Ranch Park is adjacent on part of the northern boundary and the community of Bell Canyon along the entire southern boundary.

Throughout the years, about ten low-power nuclear reactors operated at SSFL, in addition to several "critical facilities" that helped develop nuclear science and applications. At least four of the ten nuclear reactors had accidents during their operation. The reactors located on the grounds of SSFL were considered experimental, and therefore, had no containment structures.

The site ceased research and development operations in 2006. The years of rocket testing, nuclear reactor testing, and liquid metal research have left the site "significantly contaminated". Environmental cleanup is ongoing.

The public who live near the site have over the years strongly urged a thorough cleanup of the site, citing cases of long term illnesses, including cancer cases at rates they claim are higher than normal. On March 30, 2018, a 7-year-old girl living in Simi Valley died of neuroblastoma, prompting public urging to thoroughly clean up the site; despite the fact that there is insufficient evidence to identify an explicit link between cancer rates and radioactive contamination in the area.

🔗 Chemicals

Pentaborane(9) is an inorganic compound with the formula B₅H₉. It is one of the most common boron hydride clusters, although it is a highly reactive compound. Because of its high reactivity with oxygen, it was once evaluated as rocket or jet fuel. Like many of the smaller boron hydrides, pentaborane is colourless, diamagnetic, and volatile. It is related to pentaborane(11) (B₅H₁₁).

🔗 Toys

The Gakken EX-System is a series of educational electronics kits produced by Gakken in the late 1970s. The kits use denshi blocks (also known as electronic blocks) to allow electronics experiments to be performed easily and safely. Over 25 years after its original release, one of the main kits from the series was reissued in Japan in 2002.