"It's a variable-pitch propeller, which is like having gears on a bike," Land says.
“这是一个变距螺旋桨，就像在自行车上安齿轮一样，”兰德说。
2
Compression cancellous bone screw with both ends thread is a Variablepitch screw designed tO provide rigid 'fixation of cancellous bone fracture.
双端螺纹松质骨加压螺钉的特点是两端螺纹具有不同的螺距，无螺帽。
3
This paper introduces a design method of variablepitch screw, This methed make use of multinomial, bring out the boundary conditions which the design need and the operating range of the methed.