Active solar techniques use photovoltaics, concentrated solar power, solar thermal collectors, pumps, and fans to convert sunlight into useful outputs. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun. Active solar technologies increase the supply of energy and are considered supply side technologies, while passive solar technologies reduce the need for alternate resources and are generally considered demand side technologies.
What is an active solar technique used to generate energy?
designing spaces that naturally circulate air

Interstate 10, which runs southeast to northwest through town, connects Tucson to Phoenix to the northwest on the way to its western terminus in Santa Monica, California, and to Las Cruces, New Mexico and El Paso, Texas toward its eastern terminus in Jacksonville, Florida. I-19 runs south from Tucson toward Nogales and the U.S.-Mexico border. I-19 is the only Interstate highway that uses "kilometer posts" instead of "mileposts", although the speed limits are marked in miles per hour instead of kilometers per hour.
Are the speed limits on I-19 marked in miles or kilometers?
miles

At the very end of the 19th century, a new style, with a carved top and back construction inspired by violin family instruments began to supplant the European-style bowl-back instruments in the United States. This new style is credited to mandolins designed and built by Orville Gibson, a Kalamazoo, Michigan luthier who founded the "Gibson Mandolin-Guitar Manufacturing Co., Limited" in 1902. Gibson mandolins evolved into two basic styles: the Florentine or F-style, which has a decorative scroll near the neck, two points on the lower body and usually a scroll carved into the headstock; and the A-style, which is pear shaped, has no points and usually has a simpler headstock.
When was a new sytle of carved top and back construction mandolins created?
end of the 19th century