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As of the 2000 United States Census there were 40,517 people, 15,848 households, and 8,700 families residing in the city. The population density was 3,569.8 people per square mile (1,378.3/km2). There were 20,219 housing units at an average density of 1,781.4 per square mile (687.8/km2). The racial makeup of the city was 44.16% black or African American, 26.68% White, 0.48% Native American, 10.40% Asian, 0.06% Pacific Islander, 13.76% other races, and 4.47% from two or more races. 24.95% of the population were Hispanic or Latino of any race. 19.44% of the population was non-Hispanic whites.

According to the 2000 United States Census, what was the population density?
Answer: 3,569.8 people per square mile
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An early advantage of AC is that the power-wasting resistors used in DC locomotives for speed control were not needed in an AC locomotive: multiple taps on the transformer can supply a range of voltages. Separate low-voltage transformer windings supply lighting and the motors driving auxiliary machinery. More recently, the development of very high power semiconductors has caused the classic "universal" AC/DC motor to be largely replaced with the three-phase induction motor fed by a variable frequency drive, a special inverter that varies both frequency and voltage to control motor speed. These drives can run equally well on DC or AC of any frequency, and many modern electric locomotives are designed to handle different supply voltages and frequencies to simplify cross-border operation.

What is the main advantage of an induction motor?
Answer: can run equally well on DC or AC of any frequency
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For the past 25 years, the Tucson Folk Festival has taken place the first Saturday and Sunday of May in downtown Tucson's El Presidio Park. In addition to nationally known headline acts each evening, the Festival highlights over 100 local and regional musicians on five stages is one of the largest free festivals in the country. All stages are within easy walking distance. Organized by the Tucson Kitchen Musicians Association, volunteers make this festival possible. KXCI 91.3-FM, Arizona's only community radio station, is a major partner, broadcasting from the Plaza Stage throughout the weekend. In addition, there are numerous workshops, events for children, sing-alongs, and a popular singer/songwriter contest. Musicians typically play 30-minute sets, supported by professional audio staff volunteers. A variety of food and crafts are available at the festival, as well as local micro-brews. All proceeds from sales go to fund future festivals.

Where is the Tucson Folk Festival held?
Answer:
El Presidio Park