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🔗 Aviation 🔗 Military history 🔗 Military history/Military aviation 🔗 Military history/Military science, technology, and theory 🔗 Military history/World War II 🔗 Military history/German military history 🔗 Military history/European military history 🔗 Military history/British military history

The Battle of the Beams was a period early in the Second World War when bombers of the German Air Force (Luftwaffe) used a number of increasingly accurate systems of radio navigation for night bombing in the United Kingdom. British scientific intelligence at the Air Ministry fought back with a variety of their own increasingly effective means, involving jamming and distortion of the radio waves. The period ended when the Wehrmacht moved their forces to the East in May 1941, in preparation for the attack on the Soviet Union.

🔗 Italy 🔗 Classical Greece and Rome 🔗 Athletics 🔗 Highways 🔗 Road transport 🔗 Highways/European Highways

The Appian Way (Latin and Italian: Via Appia) is one of the earliest and strategically most important Roman roads of the ancient republic. It connected Rome to Brindisi, in southeast Italy. Its importance is indicated by its common name, recorded by Statius, of Appia longarum... regina viarum ("the Appian Way, the queen of the long roads").

The road is named after Appius Claudius Caecus, the Roman censor who began and completed the first section as a military road to the south in 312 BC during the Samnite Wars.

🔗 Musical Instruments 🔗 Percussion

A lithophone is a musical instrument consisting of a rock or pieces of rock which are struck to produce musical notes. Notes may be sounded in combination (producing harmony) or in succession (melody). The lithophone is an idiophone comparable to instruments such as the glockenspiel, vibraphone, xylophone and marimba.

In the Hornbostel-Sachs classification system, lithophones are designated as '111.22' – directly-struck percussion plaques.

🔗 Computing 🔗 Robotics

The Viterbi algorithm is a dynamic programming algorithm for obtaining the maximum a posteriori probability estimate of the most likely sequence of hidden states—called the Viterbi path—that results in a sequence of observed events, especially in the context of Markov information sources and hidden Markov models (HMM).

The algorithm has found universal application in decoding the convolutional codes used in both CDMA and GSM digital cellular, dial-up modems, satellite, deep-space communications, and 802.11 wireless LANs. It is now also commonly used in speech recognition, speech synthesis, diarization, keyword spotting, computational linguistics, and bioinformatics. For example, in speech-to-text (speech recognition), the acoustic signal is treated as the observed sequence of events, and a string of text is considered to be the "hidden cause" of the acoustic signal. The Viterbi algorithm finds the most likely string of text given the acoustic signal.

🔗 Central Asia 🔗 Mining 🔗 Central Asia/Turkmenistan 🔗 Turkmenistan

The Darvaza gas crater (Turkmen: Garagum ýalkymy), also known as the Door to Hell or Gates of Hell, or, officially, the Shining of Karakum, is a burning natural gas field collapsed into a cavern near Darvaza, Turkmenistan. The floor and especially rim of the crater is illumined by hundreds of natural gas fires. The crater has been burning for an unknown amount of time, as how the crater formed and ignited remains unknown.

🔗 Military history 🔗 Architecture 🔗 Military history/Fortifications

Air raid shelters, also known as bomb shelters, are structures for the protection of non-combatants as well as combatants against enemy attacks from the air. They are similar to bunkers in many regards, although they are not designed to defend against ground attack (but many have been used as defensive structures in such situations).

Prior to World War II, in May 1924, an Air Raid Precautions Committee was set up in the United Kingdom. For years, little progress was made with shelters because of the apparently irreconcilable conflict between the need to send the public underground for shelter and the need to keep them above ground for protection against gas attacks. In February 1936 the Home Secretary appointed a technical Committee on Structural Precautions against Air Attack.

By November 1937, there had only been slow progress, because of a serious lack of data on which to base any design recommendations and the Committee proposed that the Home Office should have its own department for research into structural precautions, rather than relying on research work done by the Bombing Test Committee to support the development of bomb design and strategy. This proposal was eventually implemented in January 1939.

During the Munich crisis, local authorities dug trenches to provide shelter. After the crisis, the British Government decided to make these a permanent feature, with a standard design of precast concrete trench lining. Unfortunately these turned out to perform very poorly. They also decided to issue free to poorer households the Anderson shelter, and to provide steel props to create shelters in suitable basements.

🔗 Mathematics 🔗 Statistics

In statistics, the 68–95–99.7 rule, also known as the empirical rule, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.

In mathematical notation, these facts can be expressed as follows, where Pr() is the probability function, Χ is an observation from a normally distributed random variable, μ (mu) is the mean of the distribution, and σ (sigma) is its standard deviation:

${\displaystyle {\begin{aligned}\Pr(\mu -1\sigma \leq X\leq \mu +1\sigma )&\approx 68.27\%\\\Pr(\mu -2\sigma \leq X\leq \mu +2\sigma )&\approx 95.45\%\\\Pr(\mu -3\sigma \leq X\leq \mu +3\sigma )&\approx 99.73\%\end{aligned}}}$

The usefulness of this heuristic especially depends on the question under consideration.

In the empirical sciences, the so-called three-sigma rule of thumb (or 3σ rule) expresses a conventional heuristic that nearly all values are taken to lie within three standard deviations of the mean, and thus it is empirically useful to treat 99.7% probability as near certainty.

In the social sciences, a result may be considered "significant" if its confidence level is of the order of a two-sigma effect (95%), while in particle physics, there is a convention of a five-sigma effect (99.99994% confidence) being required to qualify as a discovery.

A weaker three-sigma rule can be derived from Chebyshev's inequality, stating that even for non-normally distributed variables, at least 88.8% of cases should fall within properly calculated three-sigma intervals. For unimodal distributions, the probability of being within the interval is at least 95% by the Vysochanskij–Petunin inequality. There may be certain assumptions for a distribution that force this probability to be at least 98%.

🔗 Companies 🔗 Apple Inc. 🔗 Business 🔗 Nevada

Braeburn Capital Inc. is an asset management company based in Reno, Nevada and a subsidiary of Apple Inc. Its offices are located at 6900 S. McCarran Boulevard in Reno.

🔗 Germany 🔗 Death 🔗 Crime and Criminal Biography 🔗 Bavaria 🔗 Crime and Criminal Biography/Serial Killer

The Hinterkaifeck murders occurred on the evening of 31 March 1922, when six inhabitants of a small Bavarian farmstead, located approximately 70 kilometres (43 mi) north of Munich, Germany, were murdered by an unknown assailant. The six victims were Andreas Gruber (aged 63), his wife Cäzilia Gruber (aged 72), their widowed daughter Viktoria Gabriel (aged 35), Viktoria's children, Cäzilia (aged 7) and Josef (aged 2), and the maid, Maria Baumgartner (aged 44). They were all found struck dead with a mattock, also known as a "grub axe". The perpetrator(s) lived with the six corpses of their victims for three days. The murders are considered one of the most gruesome and puzzling unsolved crimes in German history.

Four of the dead bodies were found stacked up in the barn, the victims having been lured there, one by one. Prior to the incident, the family and their former maid reported hearing strange noises coming from the attic, which led to that maid leaving. The case remains unsolved to this day.