Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
The brushless wound-rotor synchronous doubly-fed (BWRSDF) machine is the only electric machine with a truly dual ported transformer circuit topology (i.e., both ports independently excited with no short-circuited port). The dual ported transformer circuit topology is known to be unstable and requires a multiphase slip-ring-brush assembly to propagate limited power to the rotor winding set. If a precision means were available to instantaneously control torque angle and slip for synchronous operation during motoring or generating while simultaneously providing brushless power to the rotor winding set, the active current of the BWRSDF machine would be independent of the reactive impedance of the transformer circuit and bursts of torque significantly higher than the maximum operating torque and far beyond the practical capability of any other type of electric machine would be realizable. Torque bursts greater than eight times operating torque have been calculated.
What isn't the theoretical maximum of a brushless wound rotor?
A: unanswerable

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Many pre-Columbian civilizations established characteristics and hallmarks which included permanent or urban settlements, agriculture, civic and monumental architecture, and complex societal hierarchies. Some of these civilizations had long faded by the time of the first significant European and African arrivals (ca. late 15thearly 16th centuries), and are known only through oral history and through archaeological investigations. Others were contemporary with this period, and are also known from historical accounts of the time. A few, such as the Mayan, Olmec, Mixtec, and Nahua peoples, had their own written records. However, the European colonists of the time worked to eliminate non-Christian beliefs, and Christian pyres destroyed many pre-Columbian written records. Only a few documents remained hidden and survived, leaving contemporary historians with glimpses of ancient culture and knowledge.
How do we know about some of the civilizations that were gone by the time of European arrival?
A: oral history and through archaeological investigations

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Athanasius is the first person to identify the same 27 books of the New Testament that are in use today. Up until then, various similar lists of works to be read in churches were in use. Athanasius compiled the list to resolve questions about such texts as The Epistle of Barnabas. Athanasius includes the Book of Baruch and the Letter of Jeremiah and places the Book of Esther among the "7 books not in the canon but to be read" along with the Wisdom of Solomon, Sirach (Ecclesiasticus), Judith, Tobit, the Didache, and the Shepherd of Hermas.
What books were used after his decision to standardize?
A: unanswerable

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The Tibetan Empire emerged in the 7th century, but with the fall of the empire the region soon divided into a variety of territories. The bulk of western and central Tibet (U-Tsang) was often at least nominally unified under a series of Tibetan governments in Lhasa, Shigatse, or nearby locations; these governments were at various times under Mongol and Chinese overlordship. The eastern regions of Kham and Amdo often maintained a more decentralized indigenous political structure, being divided among a number of small principalities and tribal groups, while also often falling more directly under Chinese rule after the Battle of Chamdo; most of this area was eventually incorporated into the Chinese provinces of Sichuan and Qinghai. The current borders of Tibet were generally established in the 18th century.
What empire emerged in the 18th century?
A:
unanswerable