TVC/ TVR? Time Volume Contract/ Rate?

定期定量合同?。

Background: The choice of a bioprosthetic vs a mechanical valve in tricuspid valve replacement (TVR) continues to be debated.

背景：三尖瓣置换术（TVR）应采用生物瓣膜抑或机械瓣膜的问题尚有争议。

Manufactured by TVR in 1999 the Tuscan Speed 6 sports car is equipt with an inline six engine and fiberglass body over tubular steel chassis.

1999年在TVR的制造，托斯卡纳速度6跑车配备的是与直列六缸发动机和底盘玻璃钢体在管状。