Problem: Light-emitting diode:

LEDs have been developed by Seoul Semiconductor that can operate on AC power without the need for a DC converter. For each half-cycle, part of the LED emits light and part is dark, and this is reversed during the next half-cycle. The efficacy of this type of HP-LED is typically 40 lm/W. A large number of LED elements in series may be able to operate directly from line voltage. In 2009, Seoul Semiconductor released a high DC voltage LED, named as 'Acrich MJT', capable of being driven from AC power with a simple controlling circuit. The low-power dissipation of these LEDs affords them more flexibility than the original AC LED design.

What is the efficacy of an AC powered HP-LED?
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A: 40 lm/W

Problem: Armenia:

Armenia presently maintains good relations with almost every country in the world, with two major exceptions being its immediate neighbours, Turkey and Azerbaijan. Tensions were running high between Armenians and Azerbaijanis during the final years of the Soviet Union. The Nagorno-Karabakh War dominated the region's politics throughout the 1990s. The border between the two rival countries remains closed up to this day, and a permanent solution for the conflict has not been reached despite the mediation provided by organisations such as the OSCE.

With who does Armenia have bad relations?
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A: Turkey and Azerbaijan

Problem: Incandescent light bulb:

Lamps designed for different voltages have different luminous efficacy. For example, a 100-watt, 120-volt lamp will produce about 17.1 lumens per watt. A lamp with the same rated lifetime but designed for 230 V would produce only around 12.8 lumens per watt, and a similar lamp designed for 30 volts (train lighting) would produce as much as 19.8 lumens per watt. Lower voltage lamps have a thicker filament, for the same power rating. They can run hotter for the same lifetime before the filament evaporates.

What is not effect of a thicker filament on bulb temperature?
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A: unanswerable

Problem: Heian period:

The Heian period was preceded by the Nara period and began in 794 A.D after the movement of the capital of Japan to Heian-kyo (present day Kyoto), by the 50th emperor, Emperor Kanmu. Kanmu first tried to move the capital to Nagaoka-kyo, but a series of disasters befell the city, prompting the emperor to relocate the capital a second time, to Heian. The Heian Period is considered a high point in Japanese culture that later generations have always admired. The period is also noted for the rise of the samurai class, which would eventually take power and start the feudal period of Japan.

What warrior class rose during the Heian era?
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A:
samurai