Problem: Electric motor:

To minimize overall weight and size, miniature PM motors may use high energy magnets made with neodymium or other strategic elements; most such are neodymium-iron-boron alloy. With their higher flux density, electric machines with high-energy PMs are at least competitive with all optimally designed singly-fed synchronous and induction electric machines. Miniature motors resemble the structure in the illustration, except that they have at least three rotor poles (to ensure starting, regardless of rotor position) and their outer housing is a steel tube that magnetically links the exteriors of the curved field magnets.

Why do large PM motors use high energy magnets?
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A: unanswerable


Problem: The Blitz:

Nevertheless, it was radar that proved to be critical weapon in the night battles over Britain from this point onward. Dowding had introduced the concept of airborne radar and encouraged its usage. Eventually it would become a success. On the night of 22/23 July 1940, Flying Officer Cyril Ashfield (pilot), Pilot Officer Geoffrey Morris (Observer) and Flight Sergeant Reginald Leyland (Air Intercept radar operator) of the Fighter Interception Unit became the first pilot and crew to intercept and destroy an enemy aircraft using onboard radar to guide them to a visual interception, when their AI night fighter brought down a Do 17 off Sussex. On 19 November 1940 the famous RAF night fighter ace John Cunningham shot down a Ju 88 bomber using airborne radar, just as Dowding had predicted.

What concept eventually became successful?
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A: airborne radar


Problem: Wayback Machine:

Snapshots usually become available more than six months after they are archived or, in some cases, even later; it can take twenty-four months or longer.  The frequency of snapshots is variable, so not all tracked web site updates are recorded. Sometimes there are intervals of several weeks or years between snapshots.

What is the minimum amount of time that elapses before most snapshots are released for recording?
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A: unanswerable


Problem: Republic of the Congo:

Under the 1963 constitution, Massamba-Débat was elected President for a five-year term. During Massamba-Débat's term in office the regime adopted "scientific socialism" as the country's constitutional ideology. In 1965, Congo established relations with the Soviet Union, the People's Republic of China, North Korea and North Vietnam. Massamba-Débat's regime also invited several hundred Cuban army troops into the country to train his party's militia units and these troops helped his government survive a coup in 1966 led by paratroopers loyal to future President Marien Ngouabi. Nevertheless, Massamba-Débat was unable to reconcile various institutional, tribal and ideological factions within the country and his regime ended abruptly with a bloodless coup d'état in September 1968.

When was there a coup led by paratroopers loyal to Massamba-Débat?
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A:
unanswerable