defenses

One of the factors that attracted audiences rushing to watch top-notch baseball games was the fast-paced electronic throws of up to 160km / h of first-class pitchers.

The Great Wall, China's longest defensive project, has fallen twice on the heels of the invasion of Mongol and Manchu forces.

GPS positioning technology has become familiar in life. GPS appears in the car, in the smartphone, and now is in the ... sleeve.