1. The effect of counterpressure casting parameters on secondary dendrite arm spacing ( SDAS ) of A 357 alloy was studied.

2. The essential performance had been achieved by testing through changing boundary layer ejector pumping capacity, mixing chamber clapboard length, the counterpressure, main inlet mass flux and so on.

3. This position allows you to do pelvic tilts for comfort, while giving your spouse or doula access to your back for massage and counterpressure.

4. As the top of the baby's head begins to appear, pant or blow (do not push), and apply very gentle counterpressure to your perineum to keep the head from popping out suddenly.

5. The effect mechanism of vacuum on the filling process was discussed. It shows that the vacuum can reduce the gas counterpressure in the casting mould cavity and improve the filling ability.