| 摘要 |
<p>An apparatus has a tank with an open top, a tank wall, and a closed bottom. A first ringwall extends from the bottom such that a first annular space is defined by the first ringwall and the tank wall, and a second annular space is defined by the first ringwall. A second ringwall extends in the second annular space, and defines a third annular space between the first ringwall and the second ringwall, and a cylindrical space. An air conduit extends through the cylindrical space. A pod disposed into the cylindrical space has a closed chamber and a displacement chamber. An inner riser disposed in the third annular space has an open bottom, and rests onto the inner ringwall. An outer riser rests onto the outer ringwall and is disposed in the first annular space and has a closed top, a wall, and an open bottom.</p> |
