A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed: Intake: Also known as induction or suction.This stroke of the piston begins at top dead center (T.D.C.) and ...

The Four Pests campaign (Chinese: 除 四 害; pinyin: Chú Sì Hài), was one of the first actions taken in the Great Leap Forward in China from 1958 to 1962. The four pests to be eliminated were rats, flies, mosquitoes, and sparrows.The extermination of sparrows is also known as the smash sparrows campaign (Chinese: 打 麻 雀 运 动; pinyin: dǎ má què yùn dòng) or eliminate …